An equation for the activation energy of ionic conduction in silica glasses is developed. The approach uses the classical ideas of ionic crystal theory and elasticity theory. The equation finally derived involves the radius and valence of the modifier ion, the lattice constant of the glass, the electronic charge, the shear modulus, and three arbitrary parameters. Two of these parameters are shown to be related to the geometry of the silica network and are exactly determined from difiusion of gases in glass data. The other parameter is shown to be approximately numerically equal to the dielectric constant.The theory is compared with the experimental results of 140 glass compositions.
which was completely smooth before coating, and that obtained on sandblasted metal, which was initially fairly rough. This indicates that the roughness associated with good adherence must have been developed during the firing proces.;.
V. ConclusionsThe following conclusions appear to be justified from the data presented here :(1) A positive correlation was found between the adherence of a porcelain enamel ground coat and the roughness of the interface.(2) In general, adherence correlated better with anchor points per centimeter than with the increase in interfacial area (interface ratio).(3) The method of metal preparation had a marked effect on the relation between roughness of interface and adherence of porcelain enamel ground coats to enameling iron. In general, better adherence was associated with the enamels applied to pickled iron than with those applied to sandblasted iron, for the Same degree of roughness of interface.(4) Most of the roughness that was associated with good adherence between a porcelain enamel ground coat and iron developed during the firing process.( 5 ) Roughness of interface is a necessary, but not a sufficient condition for the development of good adherence between a porcelain enamel ground coat and iron.(6) One or more factors other than roughness of interface also influences the adherence between a porcelain enamel ground coat and iron.It should be emphasized that this phase of the investigation was concerned only with a study of the relationship between adherence and roughness of interface between enamel and iron. The mechanism by which this roughness is developed will be described in a second paper.I6It is widely known that the strength of glass specimens is strongly dependent on many factors, including (1) the flaws and/or scratches on the surface, (2) the ambient atmosphere, (3) the temperature, (4) the duration of the test, and ( 5 ) the type of stress system imposed on the specimen. I n this paper the authors develop several equations that relate the average strength of glass under constant load to the duration of the test, to the temperature of the test, and to the ambient atmosphere. The data of T. C.Baker and his co-workers are used to calculate the various parameters which appear in the resultant equations. Additional experiments are suggested as a basis for further verification and/or modification of the theory.
The electrical conductivity of glass has long been known to be a function of temperature and composition, this fact being first established empirically by Foussereau in 1882. T h e temperature dependence of the resistivity would seem, however, to follow different laws at high and at low temperatures. Using the rate-process theory, a n equation is developed giving the dependence of the resistivity versus temperature. It is shown that at high and low temperatures the equation is reducible to the known empirical forms. It is also shown that glass may be nonohmic in character at low temperatures, as reported by Poole. Poole's equation for the dependence of the resistivity on field strength furthermore is shown to be a direct consequence of the theory.
In previous efforts to derive an equation for the temperature-viscosity relation of glass it has been assumed, tacitly or otherwise, that glass is a simple liquid. Since glass is not a simple liquid, it is necessary to find a model that will, in its reaction to applied stresses, have the same characteristics as a specimen of glass. By the use of Eyring's rate-process theory, such a model is proposed and several equations relating viscosity to time and to temperature are derived. The equations include an equation that relates the viscosity of any glass specimen to time, one which defines the rate of removal of internal strain, and an equation which relates the viscosity of a specimen an infinite time after beginning of a test to the temperature of the test. This final viscosity is the viscosity usually reported in the literature. It is found that the parameters in the equation reduced to infinite time can be calculated from the chemical composition of the glass and the viscosity of any given glass can be predicted at any temperature over a very wide range. Curves and tables are included to show the agreement of experiment and theoretical values.
The propagation process of longitudinal plastic pulses in prestrained bars has been studied to test the validity of the Donnell-Taylor-von Kármán theory of plastic waves. The results obtained for the propagation velocity and wave-shape changes indicate that the theory fails to describe the dynamic process by its neglect of strain-rate and creep effects.
A unified framework for quantum activated rate processes. I. General theory An equation relating the ultimate strength of glass and porcelain to time under load is derived using the rate-process theory of Eyring. The data of Preston and co-workers are used to calculate
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