Oladipo Omotoso

SOME SUCCESSFUL APPROACHES TO QUANTITATIVE MINERAL ANALYSIS AS REVEALED BY THE 3RD REYNOLDS CUP CONTEST

Details of the quantitative techniques successfully applied to artificial rock mixtures distributed for the third Clay Minerals Society Reynolds Cup (RC) contest are presented. Participants each received three samples, two containing 17 minerals each and a third containing ten minerals. The true composition of the samples was unknown to all participants during the contest period. The results submitted were ranked by summing the deviations from the actual compositions (bias). The top three finishers used mainly X-ray diffraction (XRD) for identification and quantification. The winner obtained an average bias of 11.3% per sample by using an internal standard and modified single-line reference intensity ratio (RIR) method based on pure mineral standards. Full-pattern fitting by genetic algorithm was used to measure the integrated intensity of the diagnostic single-line reflections chosen for quantification. Elemental-composition optimization was used separately to constrain phase concentrations that were uncertain because the reference mineral standards were lacking or not ideal. Cation exchange capacity, oriented-sample XRD analysis, and thermogravimetric analysis were also used as supplementary techniques. The second-place finisher obtained an average bias of 13.9%, also by using an RIR method, but without an added internal standard and with intensity measured by whole-pattern fitting. The third-place finisher, who obtained an average bias of 15.3%, used the Rietveld method for quantification and identification of minor phases (using difference plots). This participant also used scanning electron microscopy (with X-ray microanalysis) to identify minor components and verify the composition of structures used in Rietveld analysis. As in the previous contests, successful quantification appears to be more dependent on analyst experience than on the analytical technique or software used.

Mechanisms of Crude Oil–Mineral Interactions

Abstract The formation of oil–mineral aggregates (OMA) in water is initiated by a variety of physical and chemical factors that are not readily amenable to differentiation in the field or in the laboratory. This study illustrates a method that may be used to isolate the limiting parameter responsible for the formation and stabilization of OMA based on the microstructure and sedimentation characteristics of the aggregates. A flocculation index based on the sedimentation behavior of a sheared crude oil–mineral–water mixture was used to quantify the degree of interaction of oil and minerals in water. The degree of crude oil–mineral interaction was found to be dependent on the viscosity of the crude oil and the type of mineral present. Hydrophilic quartz and kaolinite interact more strongly with low-viscosity oils than with high-viscosity oils, whereas calcite (an oleophilic mineral) interacts strongly with crude oils irrespective of their viscosities. It was observed that the water chemistry must favor flocculation before the minerals can effectively stabilize oil–mineral flocs. In a fresh water analogue, quartz and kaolin interact more strongly with crude oils than montmorillonite but the reverse is true in seawater. Calcite flocculates crude oils in fresh or seawater more strongly than the hydrophilic minerals tested. In all the minerals tested, the degree of oil–mineral interaction increases and then plateaus as mixing energy is increased. Confocal laser images of the oil–mineral structures reveal two types of OMA. In low-viscosity oils with hydrophilic minerals, negatively buoyant flocs comprising minerals stabilizing oil droplets in a water-continuous phase are predominant. OMA with calcite show mineral-stabilized oil droplets and mineral-rich positively buoyant oil-continuous phase.

Centrifugation Options for Production of Dry Stackable Tailings in Surface- Mined Oil Sands Tailings Management

Water availability is beginning to impact oil sands development and, as a result, several technologies to increase the percentage of recycled water are being evaluated. One such option being re-evaluated is the use of centrifuges to produce dry tailings that can accommodate overburden and soil replacement. Previous evaluations of centrifuge performance to capture water from the clay and silt tailings (mature fine tailings) components demonstrated some success but, at the time, at unacceptable costs. A better appreciation of the long-term costs of mature fine tailings storage has prompted a re-evaluation of centrifuge technology. The use of additives to improve centrifuge performance has significantly improved the results that can be achieved. Aside from the obvious positive environmental benefit of reclaiming the fluid fine (mature fine) tailings, the increase in the amount of water recycled will reduce the demand for fresh water from the Athabasca River. This paper discusses a laboratory-scale study of the water chemistry and clay/silt feed properties affecting centrifuge performance, as well as the results of a 20 tonne per hour pilot.

The kinetics of thermal instability in nanocrystalline silver and the effect of heat treatment on the antibacterial activity of nanocrystalline silver dressings.

The kinetics of nanocrystalline silver dressing heat treatment was investigated via isothermal heat treatments at 90 degrees C, 100 degrees C, and 110 degrees C lasting 2-50h. Bactericidal efficacy of the dressings was measured via log reductions, while bacteriostatic longevity was determined via plate-to-plate transfer corrected zones of inhibition. Morphological evolution of the dressing was studied by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, while changes in heat flow were measured by differential scanning calorimetry. Increasing temperature increased the rate at which dressing bactericidal activity and bacteriostatic longevity decreased. Once changes in dressing properties began, they occurred nonlinearly with time. The earliest biological, chemical, and physical indicators of altered dressing properties were loss of bacteriostatic longevity, silver-oxygen bonds, and fine features, respectively. An early change in heat flow appeared to be responsible for these indicators, while a later change corresponded to rapid grain growth occurring after a critical crystallite size (approximately 30 nm) was reached. The grain growth exponent was determined to be 2.8 for temperatures of 100-110 degrees C, with an activation energy of 177 kJ/mol, suggesting that normal grain growth occurred, with volume and/or grain boundary diffusion as the dominant forms of diffusion. The thermal instability of nanocrystalline silver should be accounted for during production, storage, and use of dressings. The properties required for nanosilver antimicrobial efficacy demonstrated in this study, as well as its thermal instability, should be taken into consideration for the development of nanosilver products in the future.

The Use of Microscopic Bitumen Froth Morphology for the Identification of Problem Oil Sand Ores

Abstract Oil sand, which is found in various deposits around the world, consists mostly of sand, surrounded by up to 18 wt% bitumen. The largest deposits known are situated in northern Alberta, Canada, where reserves of bitumen are estimated to be 1.7 trillion barrels. Bitumen is similar to heavy oil, but with much higher viscosity and density. The two main commercial oil sand operations in Alberta are surface mines and use aqueous flotation of the bitumen to separate it from the rest of the oil sand. Under optimal conditions up to 95% of the bitumen can be recovered, but occasionally ores are mined that create problems in extraction, and recovery can drop to 70% or less. This article discusses the microscopic morphologies of various bitumen and heavy oil streams and their relationship to processing problems. The results of extensive microscopic work have demonstrated that the bitumen in an oil sand ore is the phase most susceptible to oxidation and that the resulting changes manifest themselves in particular microscopic structures. The presence and type of these structures can be related to the processing behavior of oil sand ores. Morphological features found in froths from commercial operations are similar to those found in froths from laboratory-prepared samples. The morphological features found in froths of oxidized ores have been categorized and quantified for a variety of samples and are referred to as degraded bitumen structures. Experiments in which fresh oil sand ores were subjected to low-temperature oxidation showed that bitumen froth morphology changed dramatically compared to that of nonoxidized ores for identical bulk compositions and extraction water chemistries.

Extraction and Characterization of Nano Precipitates in Microalloyed Steels

Microalloyed steels are widely used in oil and gas pipelines. They are a class of high strength, low carbon steels containing small additions (in amounts less than 0.1 wt%) of Nb, Ti and/or V. The steels may contain other alloying elements, such as Mo, in amounts exceeding 0.1wt%. Precipitation in these steels can be controlled through thermomechanical controlled processing, leading to precipitates with sizes ranging from several microns to a few nanometers. The larger precipitates are essentially TiN, with partial substitution of Nb for Ti, while the smaller precipitates are based on NbC, with Ti, Mo and V partially substituting for Nb and N partially substituting for C. Microalloyed steels have good strength, good toughness and excellent weldability, which are attributed in part to the presence of the nano-sized carbides and carbonitrides. Because of their fine sizes and low volume fraction, conventional microscopic methods are not satisfactory for quantifying these precipitates. Matrix dissolution is a promising alternative to extract the precipitates for quantification. Relatively large volumes of material can be analyzed, so that statistically significant quantities of precipitates of different sizes are collected. In this paper, matrix dissolution techniques have been developed to extract the precipitates from a series of microalloyed steels. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) are combined to analyze the chemical speciation of these precipitates. Rietveld refinement of the XRD pattern is used to fully quantify the relative amounts of the precipitates. The size distribution of the nano-sized precipitates is quantified using dark field imaging in the TEM.© 2008 ASME

Characterization of Microstructure in High Strength Microalloyed Steels Using Quantitative X-Ray Diffraction

The mechanical properties of microalloyed steels used in pipelines are strongly affected by microstructure. In this paper, X-ray diffraction (Rietveld method) was used to quantify the microstructure — specifically domain size, microstrain and preferred orientation — for four X80 steels and three experimental X100 steels. Measurements were made at the surface and at several positions below the surface. Nano-sized domains were obtained for all steels tested. A smaller domain size, higher microstrain and stronger preferred orientation were observed in the X100 samples relative to the X80 steels.Copyright

THE STRUCTURE AND THERMOCHEMISTRY OF THREE Fe-Mg CHLORITES

Chlorites are petrogenetically important minerals, exercise controls on petroleum reservoir qualities, are common in alteration zones during hydrothermal ore mineralization, and may form during carbon sequestration in sedimentary formations. Chlorite thermochemistry and structure have been investigated, in the present study, to facilitate an improved understanding of chlorite equilibria.Three natural IIb chlorites were studied by powder diffraction and calorimetric methods (low-temperature relaxation calorimetry using a Physical Properties Measurement System [PPMS] and differential scanning calorimetry [DSC]). The samples include a low-Fe clinochlore [Mg-Chl] and two Fe-rich chlorites from Windsor [Fe-Chl(W)] and Michigan [Fe-Chl(M)]. The structure of each chlorite was refined in the ideal C2/m symmetry using Rietveld techniques. Lattice parameters for theWindsor chlorite are a = 5.3786(6) Å, b = 9.3176(9) Å, c = 14.2187(6) Å, β = 96.98(10)°. The Michigan chlorite returned a = 5.3897(3) Å, b = 9.3300(3) Å, c = 14.2376(2) Å, β = 97.043(5)° whereas the low-Fe clinochlore yielded a = 5.3301(3) Å, b = 9.2231(8) Å, c = 14.2912(4) Å, β= 97.03(10)°.Heat capacities (Cp) for the three natural chlorites were measured using both PPMS (2–303 K) and DSC (282–564 K). Employing a combination of Debye-Einstein-Schottky functions, the lattice dynamics component of the Cp at lower temperature was evaluated allowing a separation of the magnetic spin ordering component of Cp from the lattice vibrational part. For Mg-Chl, Fe-Chl(W), and Fe-Chl(M), the polynomials defining the temperature dependencies of the heat capacities between 280 and 570 K are:Cp = 1185.44(±68.93) − 9753.21(±186.85)T−0.5 − 1.9094(±1.0288)·107T−2 + 3.3013(±1.5363)·109T−3Cp = 1006.06(±48.46) − 4134.83 (±1515.16)T−0.5 − 40.0949(±6.9413)·106T−2 + 5.9386(±1.0287)·109T−3andCp = 1268.60(±67.16) − 11983.09(±2107.07)T−0.5 − 7.6037(±9.6417)·106T−2 + 1.5398(±1.4187)·109T−3, respectively.Standard state molar thermodynamic functions, CP, ST, (HT−H0)/T, and φ were evaluated for the samples. S298.15 for Fe-Chl(W), Mg-Chl, and Fe-Chl(M) were found to be 499.14 ± 3.40, 437.81 ± 3.00 and 515.06 ± 3.60 J mol−1K−1, respectively, whereas S° for Fe-Chl(W) and Mg-Chl were determined to be 578.24 ± 3.76 and 503.21 ± 3.60 J mol−1K−1, −1

Crystal structure of dicalcium chromate hydrate

Direct methods and Rietveld analysis were applied to high-resolution synchrotron X-ray powder diffraction data to solve the crystal structure of dicalcium chromate hydrate (Ca 2 CrO 5 ⋅3H 2 O). The compound crystallizes in monoclinic symmetry (space group Cm, Z=2), with a=8.23575(5) A, b=7.90302(4) A, c=5.20331(3) A, and β=98.0137(3)°. The structure is built from double-layers of CrO 4 tetrahedra and CaO 8 polyhedra that run parallel to the (001) plane.