Thesis (Ph. D.)--University of Michigan, 1958.

Thesis (Ph. D.)--University of Michigan, 1958.

Molecular sieves with low silicon to aluminium ratio exhibit high ion-exchange capacity and fast exchange kinetics for the removal of divalent cations, such as Mg2 +, Ca2 + and Sr>. Owing to their unique structure and properties and the similarity of their composition to many ceramic materials, zeolites are also promising materials for use in the ceramics industry. The processing of modem ceramics formulations, e.g. glaze and coating suspensions. generally requires constant rheological characteristics over time. Glaze suspension rheology. however. usually changes with time due to the continual dissolution of the solid fraction, i.e. the frit. This study, therefore, evaluates the suitability of zeolites as ion exchangers and rheological stabilisers for the glaze industry. It is important that the zeolites in question are able to withstand the conditions of high shear and temperature experienced during ball milling without loss of crystallinity. This is detennined in this study using a variety of techniques including TGA, XRD, XRF. SEM. FTIR, zeta potential and particle size measurements. Other important properties of zeolites include their surface charge characteristics, ion exchange capacity and rheology modifying behaviour. These properties are evaluated using zeta potential, ICP. and rheology measurements respectively. Zeta potential measurements show that the surface charge properties of zeolites are a function of the silica and alumina components at the surfaces of the respective structures. i.e. the silicon to aluminium ratio. TGA, XRD, XRF, FTIR, ICP and zeta potential results show that the crystallinity of each zeolite analysed is independent of ball milling, whereas, ion exchange capacity decreases significantly after milling. The ion exchange capacity of each zeolite, however, is sufficient to cause a marked decrease in the total divalent ion concentration in the liquid phase of each glaze suspension after milling. The monovalent ion concentration in the liquid phase of each suspension may increase or decrease depending on the type of zeolite employed. The changing rheology of each suspension, on zeolite addition, also varies depending on the initial composition of the glaze components, the liquid phase ion concentration and the type of zeolite used. Time resolved measurements show that the rheology of each suspension, in the presence of zeolite, continues to change up to eight weeks after milling due to further dissolution of the glaze components. This study, therefore, concludes that although zeolites are effective at modifying the liquid phase ion concentration and rheology of concentrated glaze suspensions, they are unable to completely stabilise suspension rheology over time. The ion exchange ability of zeolites. however, may still prove to be of benefit to the glaze industry, especially in the removal of Ca2+ and Mg2+ ions from hard water sources.

No description available.

No description available.

This study presents a simplified and accurate procedure for selecting the rheological model which best fits the rheological properties of a given non- Newtonian fluid and introduces five new approaches to correct for tool joint losses from expansion and contraction when hydraulics is calculated. The new approaches are enlargement and contraction (E&C), equivalent diameter (ED), two different (2IDs), enlargement and contraction plus equivalent diameter (E&C+ED), and enlargement and contraction plus two different IDs (E&C+2IDs). In addition to the Newtonian model, seven major non-Newtonian rheological models (Bingham plastic, Power law, API, Herschel-Bulkley, Unified, Robertson and Stiff, and Casson) provide alternatives for selecting the model that most accurately represents the shear-stress/shear-rate relationship for a given non- Newtonian fluid. The project assumes that the model which gives the lowest absolute average percent error (EAAP) between the measured and calculated shear stresses is the best one for a given non-Newtonian fluid. The results are of great importance in achieving correct results for pressure drop and hydraulics calculations and the results are that the API rheological model (RP 13D) provides, in general, the best prediction of rheological behavior for the mud samples considered (EAAP=1.51), followed by the Herschel-Bulkley, Robertson and Stiff, and Unified models. Results also show that corrections with E&C+2IDs and API hydraulics calculation give a good approximation to measured pump pressure with 9% of difference between measured and calculated data.

Thesis (M.S.)--Middle East Technical University, 2003. / Keywords: Rheology, Tahin(Sesame paste), Pekmez(Concentrated Grape Juice), Blend.

No description available.

Rheological behavior of two commercial brands of stirred yogurt were investigated using a Haake RV 20 rotational viscometer. For samples from both brands, the upward shear-rate flow behavior generally followed the Herschel-Bulkley model and the downward flow curves were linear. They demonstrated progressive structural degradation with repeated shearing. In the steady shear runs, all samples exhibited apparent thixotropic behavior and did not attain the equilibrium condition even after 60 min of continuous shearing. The time-dependent stress decay behavior of all samples were accurately described by Weltman's logarithmic time model. The rheological properties of both yogurt brands were qualitatively similar. Both Arrhenius and Turian models were found suitable to assess the temperature influence in the range 10-25$ sp circ$C. / The influence of pectin (0.0 to 0.5%) and fruit concentrates (raspberry and strawberry) (64$ sp circ$B, 0 to 10%) on the rheology of stirred yogurt were evaluated. The influence of storage time at 2$ sp circ$C up to a period of four weeks on the rheological properties of the two brands were evaluated.

No description available.