High Magnetic Intensity Research Articles

Geophysical prospecting for iron ore deposit around Tajimi village, Lokoja, North–Central Nigeria

Abstract Ground magnetic and electrical resistivity survey were undertaken to investigate the occurrence and geometry of iron ore deposit around Tajimi village, Lokoja, North-Central Nigeria. The generated residual map of the ground-magnetic data acquired at 250 stations along 15 traverses revealed numerous prominent anomalies, mostly trending in the N-S direction. The radial power spectrum revealed the depth to magnetic sources between 6 m to 20 m. The interpreted VES data characterized the area into three subsurface layers: top soil, presumably iron ore layer and weathered/fresh basement. The result of vertical electrical sounding curves showed a sudden drop in resistivity (42-241 Ωm) over high magnetic response. The geo-electric section revealed that the study area is generally characterized with thin overburden (0.5-1.7 m) and the thickness of the second layer (presumed to be the iron ore layer) ranged between 6.2-25.1 m. The study concluded that areas of high magnetic intensity showed a sudden drop in resistivity value for the VES points, which give an indication of the presence of an electrically conductive structure presumed to be iron ore deposits.

Preparation and Characterization of Gold-Loaded Magnetite/Silica Core-Shell Composites

The fabrication of gold-loaded magnetite/silica core-shell particles was presented in this paper. First, 250 nm of magnetic Fe3O4 nanoparticles were prepared by solvothermal reaction. Then, the Fe3O4 particles were coated by SiO2, and Au nanoparticles (AuNPs), respectively. The core-shell structure of these microspheres was confirmed by transmission electron microscopy (TEM) and Power X-ray diffraction (XRD). The magnetic property of the core-shell microspheres was investigated at room temperature. The results indicated that the core-shell composites had a well-retained high magnetic intensity, thus it can be easily separated from the mixture in less than a few minutes by simply using a magnet.

Extension of the Archaean Madibe-Kraaipan granite-greenstone terrane in southeast Botswana: Constraints from gravity and magnetic data

The main goal of this study is to use suitably processed potential field data between longitude 24°E to 26°E and latitude 25°S to 26.5°S to gain a better geological and structural understanding of the extension of the Madibe-Kraaipan granite-greenstone terrane in southeast Botswana. Specifically, 150 new gravity measurements at 2–4 km intervals are reduced and later merged with existing gravity data in Botswana and South Africa for an integrated crustal interpretation with regional aeromagnetic data.Gravity and aeromagnetic anomalies of the region present partly coincident medium to high amplitude regions alternating with low zones. Analysis of the data revealed the existence of relatively narrow NS trending rocks of dense and high magnetic intensity extending to the village of Mmathethe, corresponding to the northern extent of the Kraaipan greenstone belt. Much of the north-central area forms a broad magnetic low and gravity high implying Kraaipan metavolcanic rocks are more extensively developed in this area than previously recognized, under a blanket of Kalahari sediments that are ∼55 m thick as indicated by borehole data. The whole area lies within an ENE-trending Pre-Transvaal dyke swarm visible on the regional aeromagnetic data and much clearer on (proprietary) high resolution aeromagnetic data. The derivative and analytic signal techniques applied for both gravity and magnetic data spatially map the greenstone belt and multiple granite plutons very well.Depth estimates obtained by the 3D Euler method in combination with two-dimensional power spectrum technique locate the high magnetic intensity horizon at around 4.0 km. The depths were further confirmed by gravity model results along two profiles across the granite-greenstone terrane in Botswana and South Africa in a W-E direction. The models show generally steep-sided bodies of comparable width with a maximum depth extent of 4.7 km for the greenstones and 4.4 km for the younger plutons. The distribution and configuration of the greenstones and plutons suggest assembly of this Kaapvaal craton western domain by plate tectonic processes. Episodic intrusion of granitoids into Kraaipan greenstone successions led to deformation of the belt with significance to Au and Au-PGE mineralization. The mapped structures could be important for groundwater exploration in this dry farming terrane.

Sub-surface structure of La Soufrière of Guadeloupe lava dome deduced from a ground-based magnetic survey

In this study, we present the analysis and interpretation of a new ground magnetic survey acquired at the Soufrière volcano on Guadeloupe Island. Observed short-wavelength magnetic anomalies are compared to those predicted assuming a constant magnetization within the sub-surface. The good correlation between modeled and observed data over the summit of the dome indicates that the shallow sub-surface displays relatively constant and high magnetization intensity. In contrast, the poor correlation at the base of the dome suggests that the underlying material is non- to weakly-magnetic, consistent with what is expected for a talus comprised of randomly oriented and highly altered and weathered boulders. The new survey also reveals a dipole anomaly that is not accounted for by a constant magnetization in the sub-surface and suggests the existence of material with decreased magnetization beneath the Soufrière lava dome. We construct simple models to constrain its dimensions and propose that this body corresponds to hydrothermally altered material within and below the dome. The very large inferred volume for such material may have implications on the stability of the dome.

Environmental conditions for the presence of magnetofossils in the Last Glacial Maximum inferred from magnetic parameters of sediments from the Ulleung Basin, East Sea

Magnetic characterization of sediments from the Ulleung basin in the East Sea (Japan Sea) was carried out to decipher changes in environmental conditions over the last ~39,000years. Magnetic susceptibility (χ), intensities of natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), partial ARM (pARM), and saturation isothermal remanent magnetization (SIRM) were measured. For selected samples, IRM acquisition, hysteresis and first-order reversal curve (FORC) measurements were made. The ratios of rock-magnetic parameters, such as χARM/χ, SIRM/ARM and S-ratio, were determined to identify magnetic grain size and mineralogical variations along with electron microscope observations of magnetic mineral extracts. Down-core variations in rock-magnetic parameters for the 5.21-m-long sediment core reveal distinct intervals with different grain size, concentration and composition of magnetic minerals. The uppermost portion and the high magnetic intensity zone (HIZ) in marine isotope stage (MIS) 2 are characterized by higher concentrations of fine-grained magnetite, whereas the MIS 1 and 3 intervals contain lower concentrations of coarser-grained magnetic minerals with increasing influence of hematite and/or iron sulphide minerals. The HIZ interval is inferred to contain high occurrences of fine-grained bacterial magnetosomes. Based on geochemical proxies, East Sea conditions for the HIZ interval, coincident with the last glacial maximum (LGM), can be summarized as having low total organic carbon (TOC), enhanced eolian contributions from terrestrial organic particles and iron-bearing minerals under the influence of an intensified East Asian winter monsoon, along with iron-reducing, but not sulphidic, conditions that favoured growth and preservation of magnetotactic bacteria. The delicate balance between reductive dissolution of magnetofossils under sulphidic conditions and production and preservation of magnetotactic bacteria in overlying iron-reducing sediments for the HIZ interval is responsible for the resultant abundance variations of magnetosomes in the studied sediments.

Effect of ZnO–B2O3–SiO2 glass additive on magnetic properties of low-sintering Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites

ZBS glasses (0.125–2.0 wt%) composed of ZnO–B2O3–SiO2 were added into the LiZnTi (Li0.43Zn0.27Ti0.13Fe2.17O4) ferrites to achieve low temperature sintering. Variations in microstructure, bulk density and ferromagnetic properties of the ferrites along with the changes of ZBS glasses concentration were discussed and analyzed in detail. Results suggest that LiZnTi ferrites mixed with appropriate amount of ZBS glass possess high saturation magnetization intensity, low coercivity, and low ferromagnetic resonance line width. Although this sintering process was completed at a low temperature (~900 °C), the ferrites still kept relatively good magnetic properties. Thus, the ZBS glass is a promising additive for low temperature sintering of LiZnTi ferrites.

Research on Magnetic Property of Nd2Fe14B/α-Fe Nanocomposite Under Different Roller Speeds

Nano-composite permanent magnetic material is a new type of permanent magnetic material, and it is the synthesis of soft and hard magnetic phase within the nanoscale. On the basis of exchange coupling hard magnetizing theory, nano-composite permanent magnetic material can, at the same time, have high residual magnetization intensity of soft magnetic phase and high coercivity of hard magnetic phase, which can be developed into new generation high performance permanent magnetic material. Nevertheless, magnetic energy of permanent nano-composite magnet derived from experiments differs greatly from the theoretical value, and this is mainly due to fairly great difference between the micro-structure of material and the theoretical model. In this paper, the constituent was taken as (Nd, Pr, Dy)2(Fe, Nb)14B/α-Fe, and the fusant rapid quenching method was adopted to study the impact of different roller speeds on the magnetic property. Moreover, through the result of VSM, XRD and SPM, the magnetic property, phase composition and micro structure of alloy were analyzed.

The advantages of a superconducting magnetic intensity greater than 1 T for phosphate–ferric flocs separation in HGMS

High-gradient magnetic separation (HGMS) is widely used for water treatment. However, the effects of high magnetic intensities on removing magnetized flocs are unclear. In this study, separating phosphate–ferric flocs via HGMS at different magnetic intensities and gradients were evaluated. The TP removal efficiencies in the 5% #1 steel wool matrix were 65.1%, 82.1%, 89.1%, and 97.5% when the magnetic intensity was 0, 1.0, 3.5 and 5.5T, respectively. The TP removal rate increased by 21.9% when the magnetic gradient increased from 6×103 to 15×103 at 5.5T. The magnetic susceptibility of flocs in 1.0-T HGMS effluents was 1.5emu/g, and saturation magnetization was not observed at 5.0T. The volume mean particle size D(4,3) of the phosphate–ferric flocs decreased as the magnetic intensity increased. Magnetite was the primary mineral phase in the 0-T HGMS effluents, whereas no mature crystals were detected in the 1.0-T HGMS effluents. Microanalysis showed that magnetite particles in phosphate–ferric flocs were captured by the steel wool matrix by the magnetic force. It is expected that some of the phosphate–ferric flocs will break into magnetite and ferric precipitates. Increasing the magnetic intensity from 1.0T to 5.5T captured more ferric precipitates, which subsequently improved the TP removal efficiency.

Suppression of the PI3K pathway in vivo reduces cystitis-induced bladder hypertrophy and restores bladder capacity examined by magnetic resonance imaging.

This study utilized magnetic resonance imaging (MRI) to monitor the real-time status of the urinary bladder in normal and diseased states following cyclophosphamide (CYP)-induced cystitis, and also examined the role of the phosphoinositide 3-kinase (PI3K) pathway in the regulation of urinary bladder hypertrophy in vivo. Our results showed that under MRI visualization the urinary bladder wall was significantly thickened at 8 h and 48 h post CYP injection. The intravesical volume of the urinary bladder was also markedly reduced. Treatment of the cystitis animals with a specific PI3K inhibitor LY294002 reduced cystitis-induced bladder wall thickening and enlarged the intravesical volumes. To confirm the MRI results, we performed H&E stain postmortem and examined the levels of type I collagen by real-time PCR and western blot. Inhibition of the PI3K in vivo reduced the levels of type I collagen mRNA and protein in the urinary bladder ultimately attenuating cystitis-induced bladder hypertrophy. The bladder mass calculated according to MRI data was consistent to the bladder weight measured ex vivo under each drug treatment. MRI results also showed that the urinary bladder from animals with cystitis demonstrated high magnetic signal intensity indicating considerable inflammation of the urinary bladder when compared to normal animals. This was confirmed by examination of the pro-inflammatory factors showing that interleukin (IL)-1α, IL-6 and tumor necrosis factor (TNF)α levels in the urinary bladder were increased with cystitis. Our results suggest that MRI can be a useful technique in tracing bladder anatomy and examining bladder hypertrophy in vivo during disease development and the PI3K pathway has a critical role in regulating bladder hypertrophy during cystitis.

Improvement of brightness of kaolin by superconducting magnetic separation and characterization of the impurities

AbstractIn the present study, changes of iron content, brightness, particle size, mineralogy and paramagnetic properties of kaolins before and after superconducting high gradient magnetic separation (SHGMS) were investigated. The Fe2O3 contents of the feed decreased by 56% after 3.5T SHGMS with 1# steel wool, but higher magnetic intensity to 5.5T did not remove additional iron. The ISO brightness of the kaolin sample after SHGMS was improved from 56.9% to 76.7%. The D50 value of the magnetic rejects was 35% larger compared to the feed. Large particles might block the micro-pores in the steel wool matrix. Compared to the feed, the dark or red impurities significantly decreased in the non-magnetic product. Paramagnetic species in the kaolin sample were sensitive to SHGMS. The resonances at g = ~2.0 and g = 4.0 decreased significantly in the concentrate compared to the feed in the ESR spectra. Iron components in the non-magnetic product were more likely to be non-paramagnetic. The results are useful for understanding the SHGMS in kaolin treatment, and might be a guide for optimizing process parameters.

Direct simulation of single bubble motion under vertical magnetic field: Paths and wakes

Motion of single Ar bubbles rising in GaInSn under vertical magnetic fields is studied numerically using a volume-of-fluid method and adaptive mesh refinement technique for two-phase interface treatment; a consistent and conservative scheme calculates induced current density and Lorentz force. Numerical results are compared with published experimental data [C. Zhang, S. Eckert, and G. Gerbeth, “Experimental study of single bubble motion in a liquid metal column exposed to a DC magnetic field,” Int. J. Multiphase Flow 31, 824–842 (2005)], where bubble diameters range from 2.5 to 6.4 mm, producing Reynolds numbers that vary between 2000 and 4000. Maximum experimental magnetic field strength was set to 0.3 T because of experimental restrictions, although we increased it to 0.5 T for firm conclusions. Apart from terminal rising velocity comparisons, we focused on variations in bubble motion paths and wake structures under magnetic fields, which cannot be observed experimentally because liquid metal is opaque. Magnetic field effects on bubble trajectory are exerted through vortex structure modification, which reinforced the conjecture that path instability is mainly attributed to wake instability. In bubble motion without magnetic fields, vortex threads in the bubble wake wrap around each other while vortex filaments incline parallel to the field with increasing magnetic intensity. Additionally, high magnetic fields will induce secondary bubble path instabilities, which contribute to the high Reynolds number flow that instabilities develop around the bubble, producing an asymmetrical Lorentz force distribution. This instability vanishes under higher magnetic intensities because flow instability is suppressed. Rising bubble aspect ratios decrease considerably under magnetic fields and may also contribute to smaller vorticities at the bubble surface. A close relationship between fluctuations in rising velocity and shape variations is found.

Multiscale analysis of high resolution aeromagnetic data for groundwater resource exploration in an arid region of South Australia

Abstract Multiscale analysis of high resolution total magnetic intensity (TMI) aeromagnetic data over a regional scale is investigated to delineate structural framework suitable for groundwater exploration in an arid region of South Australia. An innovative workflow in processing TMI data is designed, which aids in the multiscale analysis of TMI data in tilt angle domain. The rationale in considering multiscale analysis in the tilt angle domain is discussed in the paper. Each processing module of the workflow of multiscale analysis has been analyzed and the interim output in each processing step is used in the image based interpretation. An interpretation mechanism is formalized by collating digital elevation model (DEM) and geological data with the multiscale images of tilt angle anomalies of high resolution TMI data. The image based interpretation technique with multiscale analysis of high resolution aeromagnetic data has been tested successfully for groundwater resource targeting in an arid region of western Gawler Craton, South Australia. The method has been found to be an important aid in delineating structural trends, in identifying paleovalley or paleochannels and in understanding hydrogeomorphological setup of the study area.

Influence of Alternating and Static Magnetic Fields on Drug Release from Hybrid Hydrogels Containing Magnetic Nanoparticles

Hybrid hydrogels of carboxymethylcellulose (CMC), containing two different amounts of CoFe2O4 magnetic nanoparticles (50% and 70% in relation to the quantity of the polymer) as crosslinkers, were prepared. The hybrid hydrogels were chemically and morphologically characterized and their viscoelastic properties and swelling degrees were analyzed. The hydrogels were tested as controlled drug delivery systems by applying one static and two different alternating magnetic fields. The application of the two alternating magnetic fields (AMF) to the hybrid hydrogels induced a higher release of methylene blue (MB), used as a model drug, than without the application of any magnetic field, especially at low frequency (4 Hz) and high magnetic intensity (0.5 T). In contrast, when the hybrid hydrogels were exposed to a static magnetic field (SMF) the release of MB was slowed down. Furthermore the two different amounts of magnetic nanoparticles induce different responses to the magnetic field. The greater number of nanoparticles in the CMC-NP-70 hydrogel leads to the formation of some NPs clusters limiting the drug release; conversely, the CMC-NP-50 hydrogel, containing a lower amount of nanoparticles, shows a higher release of MB vs. time. In conclusion, we were able to get a potential system for modulation of the drug delivery: the release behaviour of hybrid hydrogels can be modulated by applying alternating and static magnetic fields cyclically. A possible explanation for the release mechanism is about the structural modification of the polymeric chains that occurs when the hybrid hydrogels are exposed to the magnetic fields.

Preparation of Co–Pt–P thin films by magnetic electrodeposition

Magnetic fields perpendicular to the electric field were applied during an electrodeposition process to obtain Co–Pt–P thin films from alkaline baths. Effects of different current densities and magnetic intensities on the composition, microstructure and magnetic properties of Co–Pt–P thin films were studied. It was found that the deposition rate and films thickness increased gradually with the increase of the current density and magnetic intensity. Almost all of the deposited films were crystalline and showed Co(002), CoPt(111) peaks. With the increase in the magnetic intensity, the intensity of CoPt(111) peak decreased while the intensity of Co(002) rose gradually. Magnetic fields would induce cobalt growing along (002) orientation. The films were densely covered with typical nodular structure. When the current density increased to 100 A m−2, rougher and agglomerate nodular structures would be formed. Films of smaller grain size and smooth surface could be formed under high magnetic intensity (0·5 T) as a result of impact of magnetic force and MHD effects. Furthermore, higher current density induced larger Magnetisation and lower coercivity. Largest coercivity could be achieved when current density equals to 70 A m−2. With the increase in magnetic intensity, cobalt contents in films increase gradually which lead to the rise on magnetisation.

Magnetic electrodeposition of ZnNi alloy films

Magnetic fields parallel to electrodes were introduced during plating process to obtain ZnNi alloy films from acid baths. Effects of different magnetic intensities on the composition, nucleation magnetism, surface morphology and anticorrosion of ZnNi films were investigated. With the increase in magnetic intensity, deposition rate and nickel contents increased gradually due to magnetohydrodynamic (MHD) effects caused by Lorentz force. It was found that magnetic force Fm in the magnetic electrodeposition process could have a significant effect on the mass transfer to dramatically improve deposition rate. Maximum deposition rate (90 m h−1) was achieved when the magnetic intensity was equal to 1 T. The films were densely covered with typical nodular structure. Films of smaller grain size and smooth surface could be formed under high magnetic intensity as a result of Lorentz force and MHD effects. Moreover, ZnNi films obtained with higher magnetic intensity possessed more positive self-corrosion potential and optimal anticorrosion performance. However, much higher nickel contents in ZnNi films may drop anticorrosion performance.

Aeromagnetic mapping of basement topography around the Ijebu-Ode geological transition zone, Southwestern Nigeria

Ijebu-Ode and its environs in southwestern Nigeria is located on a geological transition zone from the Precambrian migmatite gneiss rocks and Cretaceous sedimentary rock units of Abeokuta Group. Unique geological structures, complex coexistence of different rock types and poorly defined basal/lateral contacts between the basement and sedimentary rocks typify tectonic events that accompany crustal thinning and downwarping at the basement/sedimentary-basin edge. This posed serious geological decision challenges especially since it is difficult to characterize the area either as sedimentary or crystalline. Aeromagnetic data were collected, the data were filtered, inverted and enhanced using appropriate software packages and subsequently employed to generate model of the subsurface basement topography. The magnetic intensity distribution in the field ranged from −120 to +80 nT and was found to depend on the size, depth of burial and the thickness of low susceptibility superficial material overlying the magnetite rich crystalline rocks. High magnetic intensity characterized the basement rocks while lower values distinguished the metasediments rocks and sedimentary terrain. The average radial power analysis delineated shallow and relatively deep sources as the two distinct types of magnetic anomalies. Euler deconvolution results referenced to the Minna, Nigeria datum indicate depth range from −80 to +30 m for sources located below and above the mean ground level, respectively. Euler result also revealed that the depth to magnetic sources is heterogeneous and highly erratic around the transition zone, ranging between −25 and +12 m. This study identified rugged and undulating basement topography around the contact zone; it also delineated the lateral and basal contacts between the two coexisting rock types. Aeromagnetic mapping of basement sedimentary transition zone around Ijebu-Ode has proved very efficient in providing relevant information about the nature of the basement topography which provided vital information requisite for drilling and some engineering constructions decisions.

Conceptual Design of a Field Coil for 5 MW HTS Synchronous Machine

Compared with a conventional rotating machine, a superconducting rotating machine fabricated by High Temperature Superconducting (HTS) tape has superior performance and efficiency due to the HTS field coil for the rotor which can generate high magnetic flux intensity. The two primary factors for the design of the HTS rotational machine are how to construct the optimal magnetic field path through the air gap located between the rotor and the stator and how to enhance the linkage magnetic flux density between the armature coil in the stator and the field coil in the rotor. A 5 MW HTS motor for ship propulsion is planned for development in early 2011 by a Korean collaboration group of KERI and DOOSAN Heavy Industry. As a part of this R&D efforts, we designed and analyzed the field coil for a 5 MW HTS synchronous motor. In this paper, the computational results of the magnetic field distribution on the whole winding regions of the HTS field coil of the superconducting rotating machine will be also presented and discussed.

CoPtW thin films prepared by magnetic electroplating

CoPtW alloy films were prepared by magnetic electrodeposition method to replace conventional sputtering on copper substrate. The effects of different H2PtCl6 concentrations and magnetic intensities on the composition, microstructure and magnetic properties of CoPtW alloy films were investigated. With the increasing H2PtCl6 concentration, the amounts of Pt in CoPtW films increased dramatically, but the contents of both Co and W reduced gradually. Almost all of the deposited films were crystalline and contained CoPt(111), CoPt(002) and Co(002) peaks. The strongest perpendicular magnetic anisotropy could be observed when the H2PtCl6 concentration was up to 0·02 mol L−1. A higher H2PtCl6 concentration would result in bigger and agglomerate nodular structures with lots of pores. The magnetic field parallel to the electrodes during the electrodeposition process could improve the deposition rate and increase the amounts of Co in CoPtW alloy films. Magnetic fields would induce cobalt growing along the (002) orientation. Films of smaller grain size and smooth surface could be formed under high magnetic intensity (0·8 T) as a result of magnetic force and magnetohydrodynamic effects. Moreover, a transition process from hard magnetism to soft magnetism could be observed when the magnetic intensity increased from 0 to 0·8 T.

Effect of magnetic fields on pulse plating of cobalt films

Magnetic fields parallel to the electrodes were introduced during a pulse plating process to obtain cobalt thin films from alkaline baths. Effects of different magnetic intensities on the composition, microstructure, and magnetic properties of cobalt thin films were investigated. It was found that the deposition speed increased gradually with the increase of magnetic intensity. Almost all of the deposited films were crystalline and showed Co(002), Co(100) peaks. With the rise on the magnetic intensity, the intensity of Co (002) peak raised gradually. Magnetic fields would induce cobalt growing along (002) orientation. The films were densely covered with typical nodular structure. Films of smaller grain size and smooth surface could be formed under high magnetic intensity (1 T) as a result of magnetic force and MHD effects. Moreover, higher magnetic intensity induced larger saturation magnetization and lower coercivity. With the rise on magnetic intensity, cobalt contents in the films increased gradually, which led to the rise of saturation magnetization.

Preparation of NiFe films by magnetic electroplating

NiFe alloy films were prepared by magnetic electrodeposition method to replace conventional sputtering on a copper substrate. The effects of different magnetic intensities on current efficiency, throwing power and magnetic properties were investigated. Magnetic intensity played a significant role in current efficiency. When the magnetic intensity ranged from 0 to 1·0 T, the current efficiency increased from 68 to 87%. The magnetic field applied during the NiFe electroplating process would destroy the hydration state of ions in aqueous solution to increase the bath conductivity, which induced optimal throwing power. Almost all the deposited films were crystalline and formed peaks of FeNi3 (111), FeNi3 (200) and FeNi3 (220). With the rise on magnetic intensity, the intensity of all three FeNi3 peaks started to increase gradually, which induced greater crystalline. High magnetic intensity could help to obtain a smooth surface of NiFe films with small and dense particles. When the magnetic intensity ranged from 0 to 1 T, the saturation magnetisation of NiFe increased from 76 to 106 A m2 kg−1. However, the largest coercivity (7722 A m−1) could be achieved when the magnetic intensity is equal to 0·4 T.