Photoelastic Effects in Phosphate Glasses

The stress-optical coefficients of RO-Pz05 glasses (R = Mg, Ca, Sr, Ba, and Zn) were measured, and the photoelasticity mechanisms were analyzed based on the equation expressing the relation among the photoelastic constants, the elastic moduli, and the refractive index of glasses. No simple relation was found between the stress-optical coefficient and the elastic modulus, indicating that the factor (p – q), where p and q are the Neumann strain-optical coefficients, is important. The change of (p – q) with glass composition is governed mainly by changes in the effect of the atoms, rather than the lattice. The atomic effect increases with decreasing radius of the divalent cation, except for Zn²⁺. The ZnO-containing glasses exhibit extraordinarily large atomic effects. The photo-elasticity mechanism is discussed in relation to the nature of the chemical bonds.     

Kinetics of Initial Sintering with Grain Growth

Kinetic equations for initial sintering were obtained by combining the conventional kinetic equation with an empirical expression for grain growth in the initial stage. The equations describe the isothermal shrinkage of ZnO in O₂ at 80 torr and 800° to 950°C. The equation also successfully analyzed the sintering of powder compacts of Al₂O₃ studied by other workers.     

ADSORPTION BEHAVIOR OF COBALT( II) IONS ON LAYERED DIHYDROGEN TETRATITANATE HYDRATE FIBERS IN AQUEOUS SOLUTIONS IN THE RANGE FROM 298 to 523 K

The adsorption properties of cobalt(II) ions have been studied on layered dihydrogen tetratitanate hydrate fibers, H₂Ti₄O₉,?nH₂O, in the temperature range from 298 to 523?K. The distribution coefficients of the adsorption of cobalt (II) ions were increased with increasing temperatures up to 367?K, but were decreased in the temperature range between 367 and 523?K. The X-ray powder diffraction patterns of the fibers indicate that the fibers hold layer structure up to 367?K, but change to low crystalline anatase or its precursor above that temperature. It is notable that the material has the capability of cobalt (II) adsorption even at 523?K, although the maximum is present at 367?K.     

ION-EXCHANGE PROPERTIES OF HYDROUS TITANIUM DIOXIDE WITH A FIBROUS FORM OBTAINED FROM POTASSIUM DITITANATE

ABSTRACT

Ion-exchange properties of a new type of hydrous titanium dioxide with a fibrous form, which was obtained from potassium dititanate (K₂O(TiO₂)2), have been studied. The pH titration curve snowed that this material behaved as a bifunctional ion-exchanger. Distribution coefficients of some divalent metal ions on this material were measured as a function of pH and the selectivity series were found to be Ba > Sr > Ca > Mg for alkaline earth metal ions and Cu > Zn > Mn > Co > Ni for divalent transition metal ions. Large separation factors were obtained between some metal ion pairs and the mutual separations such as Cu from Sr, Ca, Mg, Co and Ni, and Mg from Ba and Zn have been achieved on columns of this material.     

Compositional Trends in Photoelastic Constants of Borate Glasses

The stress-optical coefficients of binary and ternary borate glasses were measured and the factor ( p·q ), where p and q are the Neumann strain-optical coefficients, was determined. As a modifier oxide was added to B₂O₃ glass, the stress-optical coefficient decreased monotonically. It was found that the stress-optical coefficient is determined mainly by the elastic modulus, but the factor ( p·q ) becomes significant when the content and polarizability of the modifier cation are high. It was also found that the factor ( p·q ) decreases when the content and polarizability of the modifier cation increase. The ( p·q ) was divided into the lattice effect and the atomic effect, and their compositional dependences were discussed.     

A MODIFIED RIGIDITY MODULUS TECHNIQUE FOR STUDYING THE RHEOLOGICAL PROPERTIES OF W/O EMULSIONS CONTAINING MICROCRYSTALLINE WAX

The creep compliance-time responses at constant pressure of W/O emulsions containing microcrystalline wax were determined by subjecting them to air pressure in a glass U-tube and measuring the resultant volume deformations. The constant stress at the tube wall was 2.52 times 10² dyn cm^-2. Sample slippage along the tube was avoided by blowing protuberances in the wall. Owing to the dynamic nature of the emulsions data reproducibility on a single sample could not be ascertained; with 4.0% gelatine gels reproducibility of the data was very satisfactory.     

Concurrent Measurement of Volume, Grain-Boundary, and Surface Diffusion Coefficients in the System NiO-Al2O3

Surface, grain-boundary, and volume inter diffusion coefficients for the NiO-Al₂O₃ system were measured concurrently by using a diffusion couple consisting of an A1₂O₃ bicrystal and an NiO single crystal. The A1₂O₃ bicrystals having various tilt angles were fabricated by firing 2 single crystals to be joined in an H₂ atmosphere at 1800°C for 30 h. Diffusion profiles over the surface, along the grain boundary, and in the bulk of the bicrystal were determined with an electron probe microanalyzer. Mathematical analysis of the diffusion profiles gives D _s = 7.41×10^-2 exp (-35,200/ RT ), D _gb = 2.14×10^-1 exp (-63,100/ RT ) (tilt angle =30°), and D _v = 1.26×10⁴ exp (-104,000/ RT ). The grain-boundary diffusion coefficient increases with the mismatch at the boundary.     

Inhibition of Saccharomyces Cerevisiae by Combination of Hydrostatic Pressure and Monoterpenes

Using a pressure of 1800 kg/cm₂ and 150 μg/mL of α-terpinene for 1 hr at 25°C, growth reduction of 6 log cycles after incubation at 30°C/24h, was found with S. cerevisiae. Without pressurization, S. cerevisiae was resistant to 300 μg/mL. and 600 μg/mL α-terpinene but was sensitive 1250 μg/mL. Reduction of 3 log cycles in viable cell counts was found when cells were exposed to pressure (1800 kg/cm²) and -(+)-limonene (200, 400 and 2,000 μg/mL).     

Effects of Acids on Potassium Sorbate Inhibition of Food-Related Microorganisms in Culture Media

Effects of potassium sorbate in combination with citric, lactic, phosphoric, and hydrochloric acids on the growth of six food-related microorganisms were studied. Trypticase soy broth with 0.1 or 0.2% sorbate adjusted to pH 5.5 with any of the acids was bacteriostatic to Yersinia enterocolitica 0:17. These combinations at pH 5.5 were also bacteriostatic to Salmonello group D, and extended the lag phase of Pseudomonas fluorescens for 24 hr. Combinations of either organic acid with 0.2% sorbate at pH 5.5, reduced the growth rate of Lactobacillus plantarum and an unidentified lactobacillus isolated from frankfurters. Pseudomonas aeruginosa was unaffected by any sorbate-acid combination. Organic acids, specifically citric and lactic, potentiate the antimicrobial action of potassium sorbate.     

Photoelastic Effects in Silicate Glasses

The photoelasticity of R_nO_mSiO₂(R_nO_m=Li₂O, Na₂O, K₂O, and ZnO), Li₂O-Al₂O₃-SiO₂, Na₂O-Al₂O₃-SiO₂, and Na₂O-ZnO-SiO₂ glasses was analyzed on the basis of the following equation relating the stress-optical coefficient and the strain-optical coefficient:
where C is the stress-optical coefficient, n is the refractive index, G is the shear modulus, pI2and pI1are the Pockels strain-optical coefticients, and p and q are the Neumann strain-optical coefficients. No simple relation was found between the stress-optical coefficient and the shear modulus, and the factor (p−q) was found to be an essential factor deter- mining the stress-optical coefficient of silicate glasses. It was found that (p−q) decreases markedly with increasing content of modifier oxide, and that the change of (p − q) with composition is governed by the change of the atomic effect, while the lattice effect does not change as much. It is argued that the bridging oxygen with covalent bonds increases the atomic effect and the nonbridging oxygen with ionic bonds reduces the atomic effect.