Guy E. Rindone

The internal friction of glasses

Basic fundamentals of the elastic behaviour of a standard linear solid and the internal friction technique based on this model are briefly described. The internal friction (Q−1) caused by various thermally activated processes in vitreous solids are reviewed for several glass compositions in relation to ionic mobility and other relevant properties. Similar relaxation mechanisms characterize many vitreous solids. The relaxation of alkali ions is essentially independent of the glass network former and has an activation energy of 15 to 25 kcal mol−1. Other processes like the interaction of oxygen ions and protons, alkali ions and protons, mixed-alkali ion interaction and the motion of single bonded oxygen ions have an activation energy of 30 to 40 kcal mol−1. The activation energy for relaxation of the glass network is 100 to 120 kcal mol−1.

The influence of the distribution of water in silicate glasses on mechanical relaxation

Abstract When the internal friction of an alkali silicate glass is measured at a constant frequency and as a function of temperature, three major absorption regions are found. Little doubt exists about the mechanisms responsible for the low temperature peak or for the high mechanical loss observed at higher temperatures. On the other hand, the mechanism causing the peak observed at intermediate temperatures is still open to debate. Possible mechanisms responsible for this peak are reviewed and discussed.

The hardness of PbO-ZnO-B2O3 glasses

Glasses were prepared within the ternary PbO-ZnO-B2O3 system and their microhardnesses were measured. Maxima in the hardnesses were found at about the 60 mol % B2O3 composition and were related to the glass structure. Trends of the hardnesses were explained in terms of the coordination of the boron and the effects of the PbO and ZnO on the structure as well as the void fraction within the glass. The hardnesses and the Youngs elastic moduli were observed to be related and are also discussed.

Glass in space

Abstract NASAs materials space processing program includes experiments on glass exploiting the unique microgravity environment. Among the topics are: containerless melting of new optical glasses, microballoons for thermonuclear fusion, fining, surface tension, diffusion and homogeneous nucleation.

The KIc to E relationship in phase separated glasses

Abstract Examination of the K Ic to Youngs elastic modulus relationship for structurally similar homogeneous glasses reveals that the toughness is directly proportional to Youngs elastic modulus. This can be substantiated theoretically on the basis of an elastic fracture model. If, however, the results of K Ic measurements are examined for glasses known to be phase separated in the PbOB 2 O 3 and Na 2 OB 2 O 3 systems, then a different fracture toughness to Youngs elastic modulus relationship results. Higher Youngs modulus phase separated glasses have the lower fracture toughnesses. This trend can be explained on the basis of microcracking in the crack tip process zone which shields the primary crack from the applied stress.

Glass microstructure characterization by lazer light scattering, small angle X-ray scattering and electron microscopy

Transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and laser light scattering (LLS) have been used to characterize the microstructures of mixed alkali-lithia-potassia-silica glasses and soda lime silica glasses. In most cases the three methods complement one another very well. In the mixed alkali silicate glasses LLS measurements of particle size correlate very well with TEM measurements. In addition, there is a direct correlation between particle size measurements by both methods and flaw sizes calculated from strength measurements using the Griffith equation. In the soda lime silica system LLS measurements of the glasses prior to heat treatment in the temperature region of metastable liquid immiscibility correlate very well with SAXS measurements of the heat treated glasses. The merits of each method in studies involving these glass systems will be discussed.

Gradient index glasses of macro dimensions and large Δn

Abstract Gradient index lens blanks with values of Δn up to 0.5 have been produced by fusing together thin layers of glasses of progressively different indices of refraction. Smooth, step-free gradients are formed by controlled diffusion within and across the layers. Linear, quadratic and a variety of other gradient index profiles may be produced by this method over a wide index range.

The Influence of Microstructure on Glass Strength

There is an increasing number of reports of glasses which have distinct microstructures, in contrast to homogenous but random liquid type structures. Evidence is presented that the nature of these microstructures may be influenced by the melting conditions, as well as by composition, and that the microstructure has a dominating influence on glass strength.