Hydrolysis morphology

Lees and Whitehead" have shown that differences in boiler design lead to differences in furnace atmospheres, which are subsequently reflected in differences in scale morphology and corrosion performance. Hence they report that there is no unique scale morphology which is characteristic of furnace wall corrosion. They also warn that the scale that is examined during an investigation may not be an exact reflection of the scale on the tube surfaces during operation due to the possible hydrolysis of the scale on cooling (when hot flue gas is replaced by moist air) and the redistribution of phases in the scale due to the loss of the incident heat flux. 

In semi-cristalline polymers, rate-enhancement under stress has been frequently observed, e.g. in UV-photooxidation of Kapron, natural silk [80], polycaprolactam and polyethylene terephthalate [81]. Quantitative interpretation is, however, difficult in these systems although the overall rate is determined by the level of applied stress, other stress-dependent factors like the rate of oxygen diffusion or change in polymer morphology could occur concurrently and supersede the elementary molecular steps [82, 83], Similar experiments in the fluid state showed unequivocally that flow-induced stresses can accelerate several types of reactions, the best studied being the hydrolysis of DNA [84] and of polyacrylamide [85]. In these examples, hydrolysis involves breaking of the ester O —PO and the amide N —CO bonds. The tensile stress stretches the chain, and therefore, facilitates the... 

The method used here was essentially that described by Stober et al. (4) which involves the room-temperature hydrolysis of tetra-ethylsilicate in ethanol containing varying amounts of ammonia and water, the latter two components control the final particle morphology and size. The method has been modified slightly by Bridger (2,5) and by van Helden and Vrij (3). 

In general, the structure of sol gel materials evolves sequentially as the product of successive and/or simultaneous hydrolysis and condensation and their reverse reactions (esterification and depolymerization). Thus, in principle, by chemical control of the mechanisms and kinetics of these reactions, namely the catalytic conditions, it is possible to tailor the structure (and properties) of the gels over a wide range. For example, stable silica xerogels of tailored particle dimensions, pore morphology, density and porosity, from relatively... 

ZnO particle morphologies are very complex and diversiform in comparison with Ti02. Thus, monodispersed ZnO particles with well-defined morphological characteristics, such as spherical, ellipsoidal, needle, prismatic, and rod-like shapes, have been obtained. Aggregates composed of these basic shape particles have also been achieved. The methods used for synthesis of these ZnO powders include alkali precipitation [214-216], thermal decomposition [217], hydrothermal synthesis [218], organo-zinc hydrolysis [219], spray pyrolysis [220], and other routes. 

Tepper, A.D., Ruurs, P., Wiedmer, T, Sims, PJ., Borst, J. and van Bhtterswijk, W.J., 2000, Sphingomyelin hydrolysis to ceramide during the execution phase of apoptosis results from phospholipid scrambling and alters cell-surface morphology. J. Cell Biol., 150 F5-7. 

Hematites grown hy forced hydrolysis of acidic Fe " solutions at elevated temperatures also show a range of crystal morphologies. The type of anion, the acidity and the presence of additives appear to be main factors that influence the shape (Matijevic Scheiner, 1978 Kandori et al., 1991 Bailey et al., 1993). Additives appear to act by adsorbing on specific planes of the growing crystal. At close to 100 °C, rhombohedral crystals, 50-100 nm in size, sometimes showing intergrowths (stepped appearance)... 

---