Browsing by Subject "Magnetic"
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Item The Design and Control of Stability and Magnetic Properties of Imaging Nanoparticles(2012-12) Yoon, Ki Youl; Johnston, Keith P., 1955-; Bryant, Steven L; Milner, Thomas E; Huh, Chun; Ruoff, Rodney S; Ferreira, Paulo JThere is significant interest in applying nanoparticle (NP) science to subsurface reservoirs to facilitate oil and gas recovery, image subsurface reservoirs, aid sequestration of CO2 and benefit environmental remediation. Imaging nanoparticles have been designed with long-term dispersion stability in brine and minimal retention in reservoir rock and with preferential adsorption at oil-water interfaces. Polymer-stabilized nanoparticles provide sufficient electrostatic repulsion for high colloidal stability, as characterized by the zeta potential. The small size of the clusters, superparamagnetic properties, and high salt tolerance are highly beneficial in various applications including magnetomotive and electromagnetic imaging and mapping of petroleum reservoirs. Superparamagnetic nanoclusters may be used in imaging in biomedicine and in mapping of petroleum reservoirs, by generating either ultrasonic or acoustic signals with oscillating magnetic motion. For a given magnetization per weight of iron oxide, nanoclusters with sub ~100 nm diameters experience a much larger magnetic force than that of the primary sub- 10 nm primary particles. Aqueous dispersions of 0.1-0.2 wt% superparamagnetic iron oxide nanoclusters were stabilized with citric acid, poly(acrylic acid) (PAA), or poly(styrene sulfonate-alt-maleic acid) (PSS-alt-MA) on the particle surface, with a high loading of ~90% iron oxide. For nanoclusters with only 12% (w/w) PSS-alt-MA electrosteric stabilization was sufficient even in 8 wt% NaCl. Both PAA and PSS-alt-MA were used to stabilize nanoclusters with controlled size during synthesis in aqueous media. To obtain a permanent coating on the surface of clusters cross-linking of the polymer for different cross-linking densities was applied. In this general and highly flexible approach, iron oxide nanoparticles may be formed with an adsorbed polymer stabilizer, which is then permanently bound to the surface via cross-linking. To investigate interfacial activity of nanoparticles, oil-in-water emulsions were stabilized with iron oxide nanoclusters or graphene oxide platelets. In each case, the stabilization was achieved by designing the hydrophilic/hydrophobic nature of surface coating. For oil/water emulsions, the droplet size was as low as ~1 micron diameter, and strongly shear-thinning rheology was observed. A series of sub-100 nm superparamagnetic iron oxide nanoparticles with amphiphilic poly(acrylic acid-b-butylacrylate), (PAA-b-PBA) copolymer shells was synthesized to investigate the effect of the polymer structure on the interfacial tension for nanoparticles adsorbed at the dodecane-water interface. Large reductions in interfacial tension of up to 27.6 mN/m were obtained for a 0.27 wt% nanoparticle concentration indicating significant nanoparticle adsorption and interaction with the oil and water molecules at the interface. The adsorption energy of the polymer-coated nanoparticles at the dodecane/water interface was determined from the interfacial tension and nanoparticle radius, and analyzed in terms of the structure of the polymer stabilizer. Furthermore, oil-in-water emulsions stabilized with graphene oxide nanoplatelets were found to remain stable for several months even at high salinity (up to 5 wt% NaCl, for pH = 2 to 10). The droplet sizes were as small as ~1 μm with a low nanoplatelet concentration of 0.2 wt%.Item Geophysical Fault Mapping Using the Magnetic Method at Hickory Sandstone Aquifer, Llano Uplift, Texas(2013-04-05) Pereira, Antonio Do NascimentoA magnetic study over a 95 m x 150 m area of the Hickory sandstone aquifer in central Texas was carried out as part of multitechnique geophysical investigation that included ground penetrating radar (GPR), electromagnetic (EM), seismic and seimoelectric. In geophysical exploration, the magnetic method can be utilized as an alternative to more expensive methods, such as seismic or it can be used to complement other methods. In this thesis, the magnetic method is applied to estimate the location of a previously mapped fault by Texas A&M geology students, and it is used to estimate the magnetic susceptibility contrast of the targeted fault. The main challenge of this study is imaging shallow faults using the geophysical magnetic method in a fractured aquifer with widely-scattered distribution of iron bearing rocks as in the case of the Hickory sandstone aquifer. A Geometric?G858 Cesium vapor magnetometer was used to collect magnetic data. The data consisted of 19 north-south and 1 east-west lines acquired in October and November of 2012. Elementary data processing such as diurnal correction, regional correction, reduction to pole (RTP) filter, Euler deconvolution, forward modeling and inversion were employed to characterize the faulted zone. This faulted zone separates granite basement rocks from the Hickory sandstone. As a result, this study emphasizes that Euler deconvolution applied to RTP-filtered data increases the interpretability of geological and structural contacts. The results of the magnetic method have been compared to results of GPR, EM and seismoelectric methods. Understanding the magnetic mineralogy of rocks and their properties can improve the geological interpretation of magnetic surveys.Item Magnetic control for spinning 3-unit science CubeSat(2014-12) McDonald, Karl JosephA control system is designed and validated for a 3-unit CubeSat science mission. Utilizing three magnetorquers and one reaction wheel the system achieves a 6 rotation per minute spin rate and orbit normal pointing vector of the long axis of a 3-unit CubeSat. The design is validated across an evolution of scenarios, from idealized to flight-like with expected bias and noise terms added in. Estimated mass imbalances and the limitations of the power system driving the magnetorquers force the final system design to use only magnetorquers. Considerations are also taken for the science instrument to limit the interference of magnetorquers. The overall satellite design and software implementation are also briefly discussed.Item Magnetic control for spinning 3-unit science CubeSat(2014-12) McDonald, Karl Joseph; Lightsey, E. GlennA control system is designed and validated for a 3-unit CubeSat science mission. Utilizing three magnetorquers and one reaction wheel the system achieves a 6 rotation per minute spin rate and orbit normal pointing vector of the long axis of a 3-unit CubeSat. The design is validated across an evolution of scenarios, from idealized to flight-like with expected bias and noise terms added in. Estimated mass imbalances and the limitations of the power system driving the magnetorquers force the final system design to use only magnetorquers. Considerations are also taken for the science instrument to limit the interference of magnetorquers. The overall satellite design and software implementation are also briefly discussed.Item Magnetic structure of Loihi Seamount, an active hotspot volcano in the Hawaiian Island chain(Texas A&M University, 2004-09-30) Lamarche, Amy J.The use of geophysical techniques to image the interiors of active volcanoes can provide a better understanding of their structure and plumbing. The need for such information is especially critical for undersea volcanoes, whose environment makes them difficult to investigate. Because undersea volcanoes are made up of highly magnetic basaltic rock, it is possible to use variations in the magnetic field to explore the internal structure of such edifices. This study combines magnetic survey data from 12 research cruises to make a magnetic anomaly map of volcanically active Loihi, located in the Hawaiian Island chain. NRM intensities and susceptibility measurements were measured from recovered rock samples and suggest that magnetic properties of Loihi are widely varied (NRM intensities range from 1-157 A/m and susceptibilities from 1.26 x 10-3 to 3.62 x 10-2 S.I.). The average NRM intensity is 26 A/m. The size and strength of magnetic source bodies were determined by using various modeling techniques. A strongly magnetized shield can explain most of the anomaly with a large nonmagnetic zone inside, beneath the summit. Prominent magnetic highs are located along Loihi's north and south rift zone dikes and modeling solutions suggest strongly magnetized source bodies in these areas as well as a thin, magnetic layer atop the nonmagnetic zone. The strong magnetic anomalies found along the volcano's rift zones cannot be readily attributed to recent lava flows at the surface. Instead, the source bodies must continue several kilometers in depth to give reasonable magnetization values and are interpreted as dike intrusions. Nonmagnetic anomalies at the summit and south of the summit suggest the presence of a magma system. The model solution suggests Loihi is an inhomogeneously magnetized seamount with highly magnetic dike intrusions along the rift zones with a nonmagnetic body at its center overlain with a magnetic layer.Item Modeling of recovery process characterization using magnetic nanoparticles(2013-12) Rahmani, Amir Reza; Bryant, Steven L.; Huh, ChunStable dispersions of magnetic nanoparticles that are already in use in biomedicine as image-enhancing agents, also have potential use in subsurface applications. Surface-coated nanoparticles are capable of flowing through micron-size pores across long distances in a reservoir with modest retention in rock. Tracing these contrast agents using the current electromagnetic tomography technology could potentially help track the flood-front in waterflood and EOR processes and characterize the reservoir. The electromagnetic (EM) tomography used in the petroleum industry today is based on the difference between the electrical conductivity of reservoir fluids as well as other subsurface entities. The magnetic nanoparticles that are considered in this study, however, change the magnetic permeability of the flooded region, which is a novel application of the existing EM tomography technology. As the first fundamental step, the magnetic permeability change in rock due to injecting magnetic nanoparticles is quantified as a function of particle and reservoir properties. Subsequently, a new formulation is devised to compute the sensitivity of magnetic measurements to magnetic permeability perturbations. The results are then compared with the sensitivity to conductivity perturbations to identify the application space of magnetic contrast agents. Using numerical simulations, the progress of magnetic nanoparticle bank is monitored in the reservoir through time-lapse magnetic tomography measurements that are expected. Initially, simple models for displacement of injection banks are assumed and the level of complexity is gradually increased to incorporate the realities of fluid flow in the reservoir. The fluid-flow behavior of the nanoparticles is dynamically integrated with time-lapse magnetic response. Since the nanoparticles could help illuminate the flow paths, they could be used to indirectly measure reservoir heterogeneities. Therefore, numerous case studies are demonstrated where reservoir heterogeneity could potentially be inferred. Finally, fundamental pore-scale models are developed as a first step towards the multiple fluid phases extension of the EM tomography application. Using magnetic nanoparticles to improve electromagnetic tomography provides several strategic advantages. One key advantage is that the magnetic nanoparticles provide high resolution measurements at very low frequencies where the conductivity contrast is hardly detectable and casing effect is manageable. In addition, the sensitivity of magnetic measurements at the early stages of the flood is significantly improved with magnetic nanoparticles. Moreover, the vertical resolution of magnetic measurements is significantly enhanced with magnetic nanoparticles present in the vicinity of source or receiver. The fact that the progress of the magnetic slug can be detected at very early stages of the flood, that the traveling slug’s vertical boundaries can be identified at low frequencies, that the reservoir heterogeneities could potentially be characterized, and that the magnetic nanoparticles can be sensed much before the actual arrival of the slug at the observer well, provides significant value of using magnetic contrast agents for reservoir illumination.Item Synthesis and Characterization of Piezo-Magneto (PVDF-Fe3O4) Composites(2012-07-16) Mulamba, Oliver KasongoThis research entails the synthesis and characterization of a novel class of materials which incorporate both magnetic and piezoelectric characteristics. The composite is made up of the piezoelectric polymer PVDF and magnetic nanoparticles. The testing samples are produced using a spin casting process. The characterizations of the samples were performed using X-ray diffraction, Atomic force microscopy, linear staging, Dynamic mechanical analysis, Differential scanning calorimetry, and Fourier transform Infra-Red. X-ray diffraction and Atomic force microscopy showed that the presence of the Fe3O4 particles have no effect on the crystallinity of the polymer matrix, therefore allowing for the incorporation of inclusions without directly affecting the piezoelectric property. Changes in the thermal characteristics of the polymer matrix, observed using Differential scanning calorimetry, indicated increases in the thermal conductivity of the composite. Decreases in the heat of melting and crystallization were also observed and further solidified the conclusion that the presence of the Fe3O4 nanoparticles changes the thermal behavior of the polymer. It was observed from the DMA results caused an increase in the storage modulus of the polymer matrix which is related to an increase in the material's ability to store energy. Linear staging results showed that the presence of the nanoparticles had an effect on the mechanical properties of the composites and altered the time dependent voltage output readings. These results were used to calculate the energy capabilities of the composite material and it was found that the composites showed greater energy outputs with increasing amounts of nanoparticles. Interaction was observed between the embedded particles and an external magnetic field, which was found to decrease the energy outputs of the composites. This research showed enhancements in the composite material's energy outputs in comparison to the pure PVDF samples. This research also showed that the embedded nanoparticles interacted with an exteriorly applied magnetic field. This observation introduces a new dimension of possible activation processes for piezoelectric devices which have been largely based on physical forms of activation. PVDF which is widely used in research and applications for its superior output capabilities has been enhanced in this research and shown to have capabilities to exhibit higher energy outputs.