Density, Expansivity, and Viscosity of Molten Alkali Silicates 155The fraction of total energy absorbed is defined aswhere Eh is the relative energy occurring at wave length and A h is the fraction absorbed at the same wave length and is calculated from Th (the transmission a t h) by the formula T i being for a 0.65-mm. diameter and further defined as the H. P. Gage, "Glass Color Filters for Special Applications," J . Optical Amer., 27, 161 (1937).Th fraction of impinging radiation that finally emerges in the original direction. Accordingly, due to reflection, Th = (1 -I )~ when Ah = 0; and A h = (1 -I ) when Tx = 0. The function Ah of T i plots as a nearly straight line and is simple to use when so plotted.When infrared transmission data are available for some thickness other than 0.65 mm., they can be converted either by using the expressionwhere 0 is the absorption coefficient and t is the thickness, or by the use of a 06 table published by Gage.3 Table I is a representative calculation for one of the glasses in Fig. 8 and shows (1) appropriate values for Ex and ( 2 ) that all energy beyond 5 microns, except for one reflection, is absorbed completely.densities nd vi cositie of melts in the systems LizO-SiOz, NaaO-SiOn, and K20-Si02 were measured with a restrained sphere apparatus over the temperature range 1000° to 14OO0C. At the higher temperatures in this range the density in each system decreased with increasing alkali content. On a mole basis the thermal expansivity of the potassium silicates was greater than that uf the sodium and lithium silicates. Comparisons on the basis of moles of alkali per unit volume of glass showed that to a first approximation the viscosity of the systems investigated was almost independent of the kind of alkali ion involved.
New data on the density of B2O3 from 25° to 230°C are given. A two-state equation of state for the volume is presented which fits the volume data from 350° to 1400°C. A specific structure for the two states is suggested and shown to be consistent with Raman data. Below 350°C and at high pressures the data indicated that the two-state expressions for free volume still hold but the volume of the close-packed structure becomes temperature and pressure dependent. The viscosity of B2O3 from the glass transition up to 1400°C and at high pressure is consistent with the equation of state and the hybrid equation of Macedo and Litovitz. The viscosity values above 1400°C indicate a breakup of the two-state structures and the beginning of multistate behavior which results in a temperature-dependent activation energy. The onset of this effect causes the ``apparent'' activation energy to increase above 1400°C.
The densities of liquids in the systems LizOBz03, Na20-B20,, and Kz0-Bz03 were measured by a counterbalanced-sphere method over the approximate temperature range 600" to 1000°C.The room-temperature densities of alkali borate glasses were also measured. Density increased with increasing percentages of alkali oxide below 30 mole yo. At high temperatures the densitycomposition curves showed maxima at about 30 mole yo alkali oxide. Expansivities over various temperature ranges were calculated from change of density with temperature. Expansivities in the liquid range increased with alkali content.In the low-alkali region, expansivity in the liquid range decreased with rising temperature whereas contrary behavior was noted in the high-alkali region. The most striking effect caused by the addition of alkali to Bz03 was a volume contraction. Some reasons were found to account for the lack of agreement with experimental observations of the methods of Huggins and Stevels for calculating densities.
ECEN I compilations1-3 of single crystal elastic constants do A single crystal was obtained R which had been grown from an arc melt and which gave good Laue back reflection patterns despite some variation in color.The velocity of 45 M H sound waves was measured using a pulse echo technique with the ThOz specimen mounted on the end of a vitreous silica buffer rod with stopcock grease bonds for longitudinal waves and epoxy resin bonds for transverse waves. This rod served two purposes: (1) It delayed the echoes from the specimen so that the receiver would not be overloaded when the first echo returned. (2) It simplified holding the specimen, since no electrical connections had to be made (i.e., no metallic conductive coating on the specimen was required). The bonding material could be set on the silica rod and the specimen placed on top with no holder required. A quartz transducer (x-cut for longitudinal waves, ac-cut for shear waves) was bonded to the other end of the buffer rod. The transit times were determined from the echo envelope displayed on an oscilloscope; measurements using either the peak or the leading edge agreed within the accuracy reported below. Successive echoes differed in having traversed the ThOz specimen one more round trip, but had the same number of passes through the bonds. This technique offered the advantage that transit time in the bonding material canceled out so that the difference in arrival time of successive echoes from within the Tho2 specimen could be used without correction to calculate the velocity of sound. Measurements were made along the [110] direction through 1.942 cm of specimen, and along the [liO] direction through 1.222 cm of specimen. The velocities showed no significant differences for the two directions; the standard deviations of the velocities were about 0.2% of the velocity values themselves. The accuracy is probably somewhat lower than this estimate of precision would indicate and it is felt that 0.5% uncertainty in velocity is a more reasonable estimate considering possible systematic errors in the transit time determinations. The three single-crystal elastic constants were computed as described, e.g. by de Launay4 from the velocity of longitudinal waves (a1 = 5624 m per second, of transverse waves polarized along the [OOl] direction (vz = 2824 m per second, and of transverse waves polarized along the [ IT01 direction (z13 = 3612 mper second). The resulting elastic constants in units of 10" N/m2 ( 1OI2 dyne per cmz) are c11 = 3.67 i 0.04, c12 = 1.06 f 0.02, and c44 = 0.797 i 0.008, where the plus-minus values indicate the estimated overall uncertainties. The results can also be expressed in terms of the elastic compliances in units of cm2 per dyne) and are s11 = 3.13, S I Z =-0.703, and s44 = 12.5. The bulk modulus is given by (c11 + 2c12)/3 = 1.93 X 10l1 N per ma (1 93 X loT2 dyne per cmz).The elastic anisotropy factor is given by A = 2C44/(cll -C~Z ) and has the value 0.61 for ThO2. Comparison with other fluorite structure compounds shows that CaFa6 ( A = 0.61...
The viscosity and electrical resistance of members of t h e systems Li20-B20a, Na20-Bz03, and K,0-B20s have been measured in the approximate temperature range 600' to 10QO°C. The log viscosity isotherms in the range 700" to 800°C.showed a minimum in the low-alkali region followed by a maximum as the alkali concentration was increased. This behavior could be explained by postulating a n equilibrium between two antithetical effects caused by the addition of alkali oxide to B2O3. The log electrical resistance isotherms decreased rapidly with increased alkali content up to about five equivalents of alkali ions per liter and decreased less rapidly in a linear fashion with further increase in alkali ion concentration. The equivalent conductance increased with alkali concentration, indicating behavior rather typical of liquids of low dielectric constant. The rate of increase of equivalent conductance was greater in the concentration region where the viscosity was increasing than where the viscosity was decreasing, thus illustrating that viscosity is not a controlling factor in electrical conduction. A plot of log R vs. log 7 gave straight lines whose slopes decreased with alkali content. The hypothesis that electrical resistance and viscosity of each glass were both related to the concentration of weak bonds in that glass was advanced to account for the constancy of the relation between the temperature coefficients of the two properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.