Y. Hiki

Study on the shear viscosity of several inorganic glasses

The viscosities of metaphosphate, pyrophosphate, molybdate, and fluorophosphate glasses were measured under the shear deformation mode using a sandwich method from room temperature up to the glass transition temperature Tg. An optical method was used to measure the deformation under constant load as a function of time, and the results were analyzed using a mechanical model of anelasticity plus viscosity. In glasses containing long molecular chains, two relaxations appeared at lower and higher temperatures, while only one relaxation existed at higher temperatures in glasses without the chain. Both these relaxations were of the thermal activation type. A correlation between the frequency factor and the activation energy was found for the high temperature relaxation, and the values of the frequency factor were very large. Another apparatus, a rotation disk viscometer, was also used to measure the shear viscosity above Tg. The data obtained by the two experimental methods related to each other well, and the v...

AN EXPERIMENTAL STUDY ON THE SHEAR VISCOSITY OF SOLIDS

Viscoelastic solids with high viscosity were experimentally studied with the intention of having them deformed under uniform shear stress. A kind of sandwich method was developed for applying a constant shear stress to a specimen, and its deformation was observed optically using heterodyne interferometry with a sensitivity of 10 nm in displacement measurement. Time‐dependent deformation data were analyzed on the basis of a mechanical model of anelasticity plus viscosity. Viscosity in the range of 108–1014 Pa⋅s could be determined at temperatures of 20–200 °C. Through a simulation using the finite element method together with an experiment visualizing the deformation, the specimen deformation was shown to be of an almost uniform shear mode. Experiments were performed to determine the temperature dependence of viscosity for several kinds of glasses near their glass transition Tg, and the determined viscosity values were about 107 Pa⋅s at Tg. The viscosity values measured by a rotation disk viscometer were i...

An improved transient hot‐wire method for studying thermal transport in condensed matter

The transient hot‐wire method for simultaneously measuring the thermal conductivity and thermal diffusivity of materials has been modified to improve the accuracy of the measurements. In this new experimental method, called the multicurrent method, several constant current values are used for heating the hot wire in order to determine accurately the thermal transport quantities. The details of the multicurrent method are precisely described, and examples of experiments using the method with pure water, electrolytic solution, and ionic conducting glasses are given. It is shown that this method can be used both for liquid and solid materials; a relatively small amount of the specimen material is sufficient for each experiment; the material can be insulating as well as highly ionic‐conductive; the accuracies of the determined thermal conductivity and the thermal diffusivity values are, respectively, around ±1% and ±5%.

A new apparatus for measuring high viscosity of solids

A new apparatus which is capable of measuring Newtonian viscosity as high as 108-1014 Pa · s has been developed. The upper and the lower faces of a cubic specimen 1 x 1 x I cm3 in size are respectively bonded to movable and fixed plates, and a constant shear stress is applied to the specimen. The displacement of the upper plate is measured and recorded as a function of time utilizing the HP-5528A optical laser measuring system. The sensitivity of the displacement measurement is 10 nm. Measurements at temperatures up to 200°C can be made by using a small furnace installed around the specimen. A variety of adhesive materials, polymers and ceramics, have been tested for the specimen-plate bonding. Aqueous Sauereisen cement showed a stable and rigid bonding in the experimental temperature range. Experiments for rubber (soft) and silicon crystal (hard) specimens have been performed to ascertain the reliability of the present method. The apparatus is also able to measure the anelasticity (mechanical relaxation) of solids, but is not adaptable to the measurement of the shear modulus of specimens; because the instantaneous displacement of the movable plate at the moment of the loading is mostly due to the rotational and inhomogeneous elastic deformations of the specimen.

Anelastic and viscous properties of AgI-AgPO3 glass

Abstract The anelasticity (mechanical relaxation) and the viscosity of AgI-AgPO 3 superionic conducting glass have been studied from room temperature up to near the glass transition temperature. The viscoelastic behavior was measured by shearing a cubic specimen and observing the time dependence of the shear strain using an optical method. The data were analyzed by adopting a mechanical model of standard linear solid+viscous solid, and the viscosity, the anelastic relaxation time, and the anelastic modulus have been determined. The results for the (AgI) 0.5 (AgPO 3 ) 0.5 glass were as follows. The viscosity and anelastic modulus decrease slowly and then rapidly as the temperature is increased up to the glass transition. The anelastic relaxation time is almost temperature independent, and another relaxation with a different relaxation time is superposed at temperatures close to the transition.

Viscosity of glasses near and below the glass transition temperature

The temperature dependence of the viscosity of metaphosphate glasses: (AgI)x(AgPO3)1−x (x=0.0–0.5) with low melting points has been determined near and below the glass transition temperature Tg using a method developed by the authors. In this temperature region, the viscosity–temperature relation of the glasses shows double Arrhenius equations, which have different activation energies near and below Tg, respectively. When an Arrhenius equation is applied to the observed α transition process near Tg for the glasses, the activation energy Eα appears to be proportional to Tg. The relation obtained for the glasses is Eα(kJ/mol)=(154±30)RTg(K) (R is gas constant).

Study of the thermal transport properties of superionic conducting glasses

Abstract The thermal conductivity and the thermal diffusivity of AgPO 3 and (AgI) 0.5 (AgPO 3 ) 0.5 glasses have been measured simultaneously in the temperature ranges below and above the glass transitions by using an improved transient hot-wire (multicurrent) method. Using this method, both of the thermal transport properties could be measured accurately. Special care was taken in the measurement concerning the high ionic conductivity of the materials. The temperature dependences of the two transport properties were especially noted, and apparent differences in them could be seen between two glassy materials. The experimental results were discussed on the basis of a simple phonon transport theory with special consideration of the present superionic conducting glasses.

Anelasticity and viscosity of superionic conducting glasses

Abstract The anelasticity and viscosity of AgIAgPO 3 glasses have been measured from room temperature up to near the glass transition temperature by shearing a cubic specimen under a constant load and observing the time-dependence of the shear strain by an optical method. The data were analyzed by adopting a mechanical model of the standard linear solid+a viscous solid, and the viscosity, the anelastic modulus and the anelastic relaxation time have been determined. The viscosity and the anelastic modulus decreased with temperature, while the relaxation time had no apparent temperature dependence. The results for two glasses, AgPO 3 and (AgI) 0.5 (AgPO 3 ) 0.5 , are presented and some qualitative discussions are given on the basis of the microscopic structures of materials.

Mosaic Size in Lead from X‐Ray Measurements

The size of mosaic blocks in lead powder was determined on the basis of the primary extinction effect of x rays. Integrated intensities of nine reflection lines in the Debye‐Scherrer spectrum with CuKα radiation were measured with a Geiger counter spectrometer. The mosaic size was calculated by comparing these values with theoretical values of the intensities. Correction for absorption of x rays in the specimen powder was especially important because of the large absorption coefficient of lead. The order of magnitude of the mosaic size was found to be 10−4 cm. From this value, the dislocation density was calculated to be of the order of 108 cm−2. The dislocation density decreased slightly when the specimen was annealed in vacuo at 150°C for a long time.

Nondivergence of the Viscosity of Inorganic and Polymeric Glasses near the Glass Transition Temperature

The temperature dependence of the viscosity of metaphosphate glasses and polystyrene was measured in the liquid and glass states using a method developed by the authors. The results do not show a divergence of viscosity near the glass transition temperature, Tg, which many theories predict, but do follow an Arrhenius equation below Tg. It is shown that the intermediate range order is strongly related to the glass transition mechanism. The kinetic (viscous) transition was discovered at a temperature lower by approximately 20°C than the Tg thermally determined using a differential scanning calorimeter.