Search

When phase-separated TiO 2 -bearing glasses having compositions in the cordierite primary phase volume of the CaO-Al 2 O 3 -SiO 2 -MgO system are crystallised at 1000°–1100°C, a zoned microstructure is often seen in the glass-ceramic products by scanning electron microscopy. X-ray microanalysis by the energy dispersive method has produced evidence of large-scale atomic segregation in these zones, particularly involving calcium and magnesium atoms. It is suggested that zoning has a markedly deleterious effect on some of the physical properties of these materials, particularly their strength.

The first interfacial synthesis of polyalkyloxysilanes of the form where R′ = alkylene, and R″, R = alkyl or aryl is reported. It is found, in the range studied for the stirred systems, that as organic solvent viscosity and organic phase volume are increased, rate of polymer formation is decreased. Little difference in polymer formation rate is observed when the nature of the diol is varied, but considerable difference is noted when the nature of the organosilane is varied such that the most electropositive silane has the highest rate of polymer formation. Molecular weight is approximately constant as diol is changed but varies markedly when the silane is changed, so that the silane with the most bulky substance will give polymer with the lowest molecular weight.

These computations were formulated to answer some questions concerning variations in construction and operation of countercurrent distribution apparatus. An optimum, ideal separation was simulated for passage of two compounds through a countercurrent distribution, followed by simulation of several departures from the optimum. A significant decrease in separating efficiency was found to be produced by deviation of upper-lower volume ratio from the optimum value, retainment of a portion of the upper (traveling) phase after transfer, and originally introducing solute into more than one tube before beginning the transfers. Little effect on separating efficiency was produced by randomness in tube volumes or randomness in upper (traveling) phase volumes due to time variation of solvent input. Variations in the distribution ratios can also cause significant enhancement or deterioration in separating efficiency.

A new technique is derived for determining the concentration dependence of diffusion coefficients from sorption experiments. In this analysis the diffusion equation including the effects of phase volume change and volume change on mixing is solved by a weighted residual method to produce approximate analytical expressions which describe the sorption process. It is possible to deduce the concentration dependence of the diffusion coefficient from a single sorption experiment without assuming the form of the diffusivity-concentration relationship. A direct evaluation of the technique is obtained from the analysis of test data generated by finite-difference solutions of the equations which portray the sorption process.

Liquidus temperatures in the 25% SiO 2 plane of the CaO-Nb 2 O 5 -TiO 2 -SiO 2 phase tetrahedron have been determined using the customary quench technique as well as hot-stage microscopy. The boundaries between the phase fields of CaO/sdTiO 2 , CaO/sdTiO 2 /sdSiO 2 , TiO 2 , SiO 2 , CaO·Nb 2 O 5 , CaO·SiO 2 , 10 CaO·Nb 2 O 5 ·6 SiO 2 (niocalite) and 2 CaO · SiO 2 have partly been outlined. This 25% SiO 2 plane probably also includes phase fields for 3 CaO·SiO 2 and CaO. A phase field of CaO· SiO 2 is wedged in between those of CaO · Nb 2 O 5 and 10 CaO· Nb 2 O 5 ·6 SiO 2 (niocalite), instead of a field of 2 CaO · Nb 2 O 5 , as is found in the 20% SiO 2 plane. This would be expected from the known CaO-Nb 2 O 5 -SiO 2 phase diagram. All three compounds, 2 CaO· Nb 2 O 5 , CaO·Nb 2 O 5 and 10 CaO· Nb 2 O 5 ·6 SiO 2 , apparently occupy similar phase volumes between the CaO-Nb 2 O 5 -SiO 2 side and the large phase volume of CaO · TiO 2 (perovskite), in the quaternary system. A summary of the phase relationships studied in the CaO-Nb 2 O 5 -TiO 2 -SiO 2 system is given, and also some discussion of the mineralogical implications of these studies.

SUMMARY A phase inversion temperature (PIT) system for selecting an emulsifier has been developed and compared with the HLB-value system. The hydrophile-lipophile balance (HLB) of a nonionic surfactant changes with the temperature and the inversion of an emulsion type occurs at which these two properties just balance. The PIT changes with the experimental conditions and affords information on the types of oils, the phase Volume, the concentration of emulsifiers, the effect of temperature etc., but the HLB-value does not afford such information. PIT is also closely related with the other properties.

The effect of phase volume on the phase inversion temperature (PIT) of emulsions stabilized with nonionic surfactant has been studied. In emulsions composed of saturated hydrocarbons (halogenocarbons) and water, the PIT was nearly constant for a wide volume-fraction range, indicating a marked effect of temperature on the emulsion types. The longer the hydrophilic chain length of the surfactant, the higher the PIT.

Schairer's study (1954) on phase relations in the system KalSi2O6–Mg2SiO4–SiO2 was extended to include the system KalSiO4–Mg2SiO4–KalSi2O6. It is shown that this join is ternary; however, the relatively high vapor pressure of the condensed phases prohibits study by the usual quenching techniques. The apparent intersection of the (KalSiO4–Mg2SiO4–SiO3) join with the primary phase volume of spinel is attributed to loss of the alkali-silicate constituents by vapor transport. This results in the effective bulk composition being moved away from this join toward the primary phase volume of spinel in the system K2O–MgO–Al2O3–SiO2.

The conductivities of dispersions are studied theoretically and experimentally. Data on foams, emulsions, and mixtures of solids in liquids indicate that the dilute suspension relations are not obeyed above a dispersed phase volume fraction of about 0.2. A review of previous attempts at predicting the behavior of the data at higher concentrations reveals need for improvement both in regards to experimental accuracy and theory. Electrical-conductivity data on emulsions are presented where the conductivities of the two phases vary over a wide range and where the volume fraction of the dispersed phase extends up to 0.6. In addition measurements are made on dispersions of ordered arrangements of spheres and cylinders. Theoretical developments are presented following three different methods of attack. The mathematical technique used by Bruggeman for dispersions of spheres is employed to develop an expression that is valid for dispersions of spheroidal particles. A new approximation (distribution model) is proposed for treating a concentrated dispersion of spherical and nonspherical particles. The resulting expression is in good agreement with measurements on spheroidal particles over the entire range of concentrations. The Rayleigh equation for the conductivity of a cubical lattice of spheres is redeveloped by uning a different potential function and consideringmore » higher terms. (auth)« less

The effects of dispersed phase volume and temperature on the batch growth of Candida lipolytica on gas oil are investigated. Growth parameters are presented for two sets of experiments. The shape of growth curves was basically similar to the system composed of n-hexadecane dissolved in dewaxed gas oil, in spite of the complex nature of the substance. All of the batch growth curves exhibited a linear growth region. The rate of linear growth and its length varied with change in dispersed phase volume. The effect of temperature on growth rate was investigated for temperatures ranging from 23°C to 34°C. The results show a smaller activation energy during linear growth than during the early stages of batch growth. These results are analyzed from the viewpoint of growth models presented previously. The results indicate that growth at drop surfaces is important and that segregation effects may be important.

The effects of inoculum size, dispersed phase volume and substrate concentration on the batch growth of Candida lipolytica are investigated in a model system composed of n-hexadecane dissolved in dewaxed gas oil. Tabular values and parameters are presented for 16 different experiments. All of the batch growth curves exhibited a linear growth region with the length of the region ranging from 1.5 to 9.5 hours. The rate of linear growth varied both with change in dispersed phase volume and initial dispersed phase substrate concentration. A qualitative analysis of the results is presented and possible explanations for the observed linear growth rates are discussed.

Publisher Summary The three-body resonance is defined by the resonance above the threshold of the three-body break-up channel. Experimentally, the three-body resonance is found by comparing the energy spectrum of the spectator particle with the phase volume. The R-matrix theory, which is so successful for the analysis of two-body resonances, cannot be applied to the three-body resonances. Finding the three-body resonance is a challenging business also for a theorist: Once a theory of the three-body resonance is established, it serves to predict three-body resonances, whose experimental finding is usually not easy. A theory that yields the three-body resonance must satisfy the general properties of the S-matrix. This chapter presents the recapitalization of three-body resonance theory, then describes its application to the three-nucleon system in which the antisymmetrization is taken into account, and describes a preliminary result of numerical calculations. It also explains the method to treat the resonance of the four-body system.

In thermodynamics the difference in entropy of two states I and II is given by $${S_{II}} - {S_I} = {\left( {\int\limits_I^{II} {\frac{{\delta Q}}{T}} } \right)_{rev}}$$ (73.1) where δQ is the heat supplied. The index “rev” means that the transition from I to II has to be carried out in a reversible way. If the quantum mechanical ground state E0 of the system is nondegenerate, the quantum theoretical phase volume Φ(E) approaches 1 for E just above E0, which means that the entropy, S & klnΦ, approaches zero. The entropy of the ground state can then be normalized to zero and one can define an absolute value of S by starting from the ground state E0 or from \(T = 0\left( {{S_1} = {S_{{E_o}}} = 0} \right)\): $${S_{II}} = \int\limits_I^{II} {\frac{{\delta Q}}{T}} $$ (73.1a) .