Homogeneous thin films of zinc titanate have been successfully prepared on Si(100) wafers by depositing a film of zinc and titanium oxides (ZnO‐TiO2) by low‐pressure metalorganic chemical vapor deposition (MOCVD), followed by an annealing treatment. The precursors used for the deposition were diethylzinc (DEZ), tetraisopropoxide titanium (TPT), and water. By performing the deposition at temperatures between 140 and 350C, the stoichiometry of the as‐deposited films could be effectively controlled over Zn/Ti ratios between 0.5 and 2.5, which cover the composition of various zinc titanate phases identified in the literature. The as‐deposited ZnO‐TiO2 films are amorphous, and possess a fairly smooth surface. XPS and SIMS analysis showed that the composition of these films is uniform over the wafer as well as through the films bulk. An annealing treatment of the as‐deposited films at high temperature
In commercial slabstock foaming, liquid CO 2 technology is increasingly applied to replace previously used liquid auxiliary blowing agents like CFCs and methylene chloride. Knowledge of physical properties of mixtures which are used in liquid CO 2 foaming may contribute to the further development of the liquid CO 2 technology.Equations have been determined which do predict, for specific operational conditions and formulations, the pressures which are required in commercial foam operation to keep the CO 2 dissolved both in the polyol/CO 2 and in the foaming mixture/CO 2 solutions. The evident dependence on temperature of CO 2 solubility, established for both polyol and foaming mixtures, strongly supports tight temperature control of the feedstocks in slabstock liquid CO 2 foaming.The solubility of CO 2 in polyol was found to increase with the EO content of the polyol where the effect of molecular weight was found to be negligible.It was established that small amounts of water and surfactant lower the CO 2 solubility, and it is predicted that the commonly used levels of TDI do the same. Based on this information, it is advisable to conduct the mixing of TDI and auxiliary components at pressures a fraction higher than the saturation pressure of the liquid CO 2 polyol mixture.A significant decrease of both viscosity and surface tension is quantified for polyol and model foaming systems at increasing liquid CO 2 concentration. These Downloaded from decreases may explain why very small cell sizes can be obtained with liquid CO 2 foaming, as the nucleation process takes place at high liquid CO 2 concentration. The rise in viscosity upon evaporation of CO 2 into the froth may explain the relative stability of the unreacted froth.A cooling capacity of about 1°C per part of CO 2 per hundred parts of polyol is determined from two independent experiments. However, for safety reasons, it is advisable to keep the current assumption of 0°C per part of CO 2 per hundred parts of polyol in commercial foaming until a further study on the temperature evolution of liquid CO 2 blown foaming under practical conditions is conducted.
The use of reactive transport modeling (RTM) is increasing in the oil and gas industry for assessing the geochemical impact (e.g. scaling and souring) of various activities, such as waterflooding for improved oil recovery (IOR) and CO2 storage. RTM is a technique that integrates fluid flow, transport of heat and solutes, and geochemical reactions. It can be used to model fluid compositional changes as well as rock mineralogical changes, caused by geochemical reactions, under flowing conditions. We use our in-house reservoir simulator (MoReS), coupled to geochemical software (PHREEQC), to carry out RTM. Simulations are based on the mixed solvent electrolyte (MSE) model from OLI Studio, a standard tool used by production chemists, enabling accurate computation of aqueous chemical reactions and partitioning of components between solid, fluid and gas phases. Over the last few years we have used RTM to make scale predictions for several waterflooding projects around the globe. In this paper we will show results from these field cases and highlight the most important findings. In brief, these are: Enabling mineral precipitation reactions in flow calculations improves the match between measured and simulated production water (PW) chemistry.Full 3D reservoir models capture different flow paths arriving/mixing near production wells, enabling an improved match between historical and simulated PW chemistry. Simplified (1D/2D) models are sufficient for predicting the magnitude of scale deposition and screening scale prediction uncertainties when little is known about reservoir connectivity (e.g. new developments).Inclusion of clay mineral cation exchange reactions significantly modifies the evolution of the injected water composition during migration through the reservoir. As a result, this impacts the reservoir deposition of scaling minerals (e.g. barite) and the scaling potential of production wells. Characterization of cation exchange properties of clay minerals in reservoirs is therefore recommended. The developed workflow, based on learnings from various projects, is now used to forecast scaling risks in new projects and supports ongoing projects in mitigating risks (e.g. selection/timing scale squeezes).
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