Solution aging

For other discussions of two-phase models and numerical solutions, the reader is referred to the following references thermofluid dynamic theory of two-phase flow (Ishii, 1975) formulation of the one-dimensional, six-equation, two-phase flow models (Le Coq et al., 1978) lumped-parameter modeling of one-dimensional, two-phase flow (Wulff, 1978) two-fluid models for two-phase flow and their numerical solutions (Agee et al., 1978) and numerical methods for solving two-phase flow equations (Latrobe, 1978 Agee, 1978 Patanakar, 1980). 

In the following sections, synthesis of the anionic polymers, copolymer molecular weight, limiting viscosity number, electrolyte effects, solution shear thinning, screen factor, polymer radius of gyration, and solution aging will be discussed and data on the copolymers presented. 

Goldstein etal. (1959) studied me effect of solution aging on me effectiveness of PE resins to improve wood properties. An analysis of a laboratory prepared PE solntion was made over a total of 135 days, which showed that mere was initially an increasing... 

The progress toward re-equillbratlon of all of the dilute solutions aged for up to 25 days at 23 C Is shown In Figure 2. 

Figure 2. Solution pH versus solution age. Aluminum concentra-tion (C), 0.005M ( ), 0.040M (+), 0.058M ( ), 0.061M (0),...

Figure 3. PILC surface area versus solution age. See Figure 2 for symbols.

Figure 4. Surface area versus A1 concentration. Solutions aged for 0 days ( ), 10 days (+) and 25 days (A).

Catalyst PILC from 0.3M A1 solution aged 7 days, calcined S.A. = 270 mVo Feed North Sea gas oil. 

The surface areas of pillared clays prepared from dilute Chlorhyd-rol solution depend on the extent of dilution and age of the dilute solution. Dilution produces polycations favorable to the production of pillared clays by depolymerizing larger polycations present in the Chlorhydrol solution. Aging is the reequilibration of these depolymerized solutions. 

Hydrolysis of FeCf Solutions. Aging of ferric chloride solutions yields, as a rule, either colloidal akageneite (p-FeOOH) or hematite (a-Fe203). However, the two forms are closely related in the formation of the precipitates (95,142). 

Reference 100 described a different technique than usual, in that it used elemental S dissolved in a carboxylic acid. Propionic acid was most often used, although other carboxylic acids could also be employed. It was noted that best results were obtained when the SnCl2 was added as a powder to a freshly prepared S solution aged solutions reacted much more slowly, if at all. It was surmised that this was due to changes in the nature of the dissolved Sn with time, such as tin oxide, or propionate formation and loss of HCl. 

All solutions were stored for 60 days before use. This delay was necessary for accurate results since Narkis (10) had already shown that poly(l-amidoethylene) solutions are not molecularly disperse until 54 days after preparation. These solutions age by losing intermolecular entanglements and becoming monomolecular solutions (10). Poly( 1-amidoethylene) solutions are known to lose viscosity with time (11). Several authors have attributed this viscosity loss to oxygen or radical degradation of the polymer (11), but Francois (12) has shown that changes in viscosity only... 

Although the general effect of the addition of bicarbonate was to increase the size of the colloidal species, Lindenbaum and Westfall obtained the opposite effect with citrate addition over the pH range 4-11, as measured by the percent of plutonium (IV) that was ultrafilterable (22). However, their plutonium concentrations were 2 X 10 5Af, and the solutions probably contained true colloids, rather than pseudocolloids, if one accepts Davydovs analysis. Lindenbaum and Westfall concluded that the mechanism of the citrate action was the complexation of plutonium, thereby preventing the formation of hydrolytic polymers. It should be noted, however, that even with a citrate-plutonium molar ratio of 1800 (3.4 X 10 4Af citrate), about 10% of the plutonium still could not pass through the ultrafilter for solutions aged up to four days (22). 

Aluminum. Matijevic and Tezak (27) found that solutions of AF in 10"4 to 10-fiAf range were unstable (unless acid is added) and that such solutions age unpredictably with time. They can be artificially aged by heating to 90°C., producing rather large polymeric cations which are difficult to return to simple Afv with acid at room temperature. At 10-1 to 10"sAf concentration the author and co-workers are currently engaged... 

Abstract Polyferrocenyldimethyl-silane (PFS) diblock copolymers with polyisoprene (PFS-PI) or with polydimethylsiloxane (PFS-PDMS) self-assemble in simple alkane solvents to form what appear by TEM to be dense flexible cylinders (nanowires) or nanotube-like structures. Typical widths are on the order of 20 to 30 nm, with variable lengths often greater than 10 un. The structures that form, and the dimensions of the tube-like structures or wires, depend upon the composition of the polymers and the lengths of the blocks. Light scattering experiments show that the PFS-PDMS (block ratio 1 12) solutions aged... 

Figure 4.14 Nitrogen adsorption isotherm for a SAW device dip coated using a sol containing four oxide precursors ( four component ). This coating was prepared from a solution aged for two weeks at S0°C and pH 3. The large amount of adsorption relative to the film thickness and the Type IV isotherm shapie indicate that this film is highly porous. (Reprinted with permission [lo] by counesy of...

Vaughan et al. (2) found that, due to further polymerization of the pillaring cations, hydrothermal treatment of the aluminum chlorohydrate solution (reflux conditions) used in the preparation of the pillared smectites resulted in a material with improved hydrothermal stability. Tokarz and Shabtai (H) conducted a similar study using base hydrolyzed AlCl3-solutions. They found that refluxing of the solutions for 6- 8 hr. was sufficient to produce pillared smectites with improved thermal stability and higher porosity as compared with those prepared from solutions aged at room temperature for two weeks. 

Fig. 27. Efficiency of excited state formation (f>ts (data from [197]) as a function of the reaction exothermicity AGe for the ECL system Mo6Cl]7/D+ ( ), MosClJi/A- (O) and MosClJ /R (O) in acetonitrile solutions. AGe values are calculated from the difference in the standard redox potentials corrected for the Coulombic interactions between reactants and products.

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