Magnetic Particle Size Research Articles

Relationship between mineral magnetic properties and soil textural parameters

The study analyzed the relationship between mineral magnetic properties and particle size in order to determine the suitability of magnetic measurements to serve as particle size proxy for urban top soils samples collected from Jalingo, NE Nigeria. Pearson correlation analyses between mineral magnetic parameters (χlf, χfd%, χARM, SIRM, Soft IRM, ARM/SIRM) and particle size properties (PM2.5, PM10, clay, silt and sand) are reported. Results indicate that each particle size class shows different strength of correlation with magnetic parameters, implying that each particle class contains a proportion of magnetic minerals. For the whole data set (n = 154), χfd%, χARM and ARM/SIRM show significant positive correlation with the fine size fractions (PM2.5, PM10, clay and silt) but negatively correlated with the sand proportion, while χlf, SIRM and Soft IRM exhibit contrasting relationship. Of all the magnetic parameters, the magnetic parameters indicating fine-grained ferrimagnetic minerals (ARM/SIRM and χARM) have the strongest and most significant correlations. The nature of the magneto-particle size relationship is different when examined in terms of land use. The fact that magnetic properties and textural parameters have strong relationship indicates that magnetic methods could be considered a potential particle size proxy in Jalingo. However, since the relationship does not follow predictable and consistent patterns of other studies in top soils and sedimentary settings, it brings to fore the non-universality of the method. Hence, the type of relationship existing between magnetic and particle size properties in an environmental setting must be determined before applying the magnetic method as particle size proxy.

Synthesis of PEI-Functionalized Magnetic Nanoparticles for Capturing Bacteria

Polyethyleneimine (PEI) functionalized Fe3O4 MNPs were synthesized by a modified hypothermal oxidative hydrolysis method. The magnetic nanoparticles showed positively charged surface, strong magnetic responsivity and uniform particle size distribution at 56.1±0.6 nm. Aggregation of these magnetic nanoparticles were observed on the surface of different type of bacteria. Magnetic capturing of bacteria were facilitated by these magnetic nanoparticles. The capturing efficiency could reach 90% after two rounds of interactions of 5 minutes. The mechanism and process of interactions between bacteria and polyethyleneimine functionalized Fe3O4 magnetic nanoparticles were explored and discussed. The present study not only provides insight into interactions between Fe3O4@PEI MNPs and bacterial cells, but also opens a new avenue for designing and applying Fe3O4@PEI MNPs as biosensors in microbiology, medicine, and environmental science.

Study on the magnetic abrasive finishing process using alternating magnetic field: investigation of mechanism and applied to aluminum alloy plate

In order to achieve the finishing of complex microsurface, the magnetic abrasive finishing process using alternating magnetic field was proposed. In this paper, the mechanism of the magnetic abrasive finishing process using alternating magnetic field was investigated. At the same time, the influence of magnetic particle size and magnetic field frequency on magnetic cluster changes was observed and the relationship between finishing force and alternating magnetic field was analyzed. In addition, the feasibility of ultraprecision finishing of 5052 aluminum alloy plate through this process was studied, and the influence of relevant process parameters on the finishing characteristics was analyzed. The experimental results show that the surface roughness of 5052 aluminum alloy plate improved from 318 to 3 nm Ra in 15 min.

New insights into the magnetic characteristics of high mountain loess in Central Asia and its paleoclimatic implications

The previous studies applied “wind intensity” model to explain the corresponding variations of magnetic susceptibility and particle size curves in Tienshan Mountain loess. Most of these studies focused on low altitude loess, due to their high deposit rate, and ignored the high-altitude loess. In this study, we investigated characteristics of lithological and pedogenic magnetic particles to systemically understand their paleoclimatic implications. The result suggested high mountain loess in Tienshan region exhibits that, not only lithologic magnetic particles, but also pedogenic present the variable contents. The magnetic susceptibility has a complex implication. In contrast, the fine-grained magnetite exhibits a close link with pedogenesis. Therefore, the relative parameters can be used to recover moisture variation. The evidences from particle size and their dependence of magnetic susceptibility suggested particle-size effect on lithological magnetic susceptibility is weak. The “wind intensity” model can be an important factor for variations of lithologic magnetic susceptibility of Tienshan Mountain loess rather than a dominant factor. It still needs more study to determine the implication of magnetic susceptibility of lithologic materials.

Innovative released-active drug for the treatment of neurological diseases: Results of preclinical studies

A numerical inversion method known from the analysis of light scattering by colloidal dispersions is now applied to magnetization curves of ferrofluids. The distribution of magnetic particle sizes or dipole moments is determined without assuming that the distribution is unimodal or of a particular shape. The inversion method enforces positive number densities via a non-negative least squares procedure. It is tested successfully on experimental and simulated data for ferrofluid samples with known multimodal size distributions. The created computer program MINORIM is made available on the web.

Estimation of Intrinsic Magnetic Properties of Single Particles by Particle Tracking Velocimetry

Characterization of paramagnetic particles is of utmost importance in biotechnology, cell separations, and medical applications. The particle size uniformity and colloidal stability of paramagnetic particles have been the focus of most producers, but magnetization is never specified and is typically mentioned only in terms of percent iron oxide content. Bulk measurements of magnetic susceptibility and saturation magnetization, using a superconducting quantum interference device (SQUID) or a vibrating sample magnetometer (VSM), provide an average value at best and do not account for the distributed nature of these variables or for particles with zero or very low susceptibility and magnetization. By means of particle tracking velocimetry in dark-field illumination, we measured multiple characteristics of several thousand individual micrometer-sized particles per sample. The Hyperflux velocimeter is utilized to provide quantitative video analysis of cells and particles using a high-definition camera to capture the images of the particle trajectories in an isodynamic field. Image analysis software converts the image data to the parameters of interest based on velocimetry calculations. The intrinsic magnetic properties of the magnetic beads estimated by both the velocimeter and VSM are in good agreement. Estimation of the magnetophoretic mobility distributions and intrinsic magnetic properties of magnetic microparticles using dark-field particle tracking allows economical and time-efficient magnetic evaluation of a broad range of magnetic particle sizes.

Isolation and separation of Listeria monocytogenes using bacteriophage P100-modified magnetic particles

A bacteriophage-assisted magnetic separation method was developed for the isolation of Listeria monocytogenes from complex food matrices. The aim of this study is to understand the effect of phage immobilization methods and the magnetic particle sizes on the phage coupling and infectivity retention of the magnetic particles. In this study, bacteriophage P100-modified magnetic particles (PMMPs) were developed for the separation of L. monocytogenes from food matrices. Three sizes of magnetic particles (MP) (150 nm, 500 nm, and 1 μm) were used for phage immobilization via chemical and physical methods. The coupling ratio of phage was investigated, and the performance of each PMMP complex was evaluated by their L. monocytogenes capture efficiency. When compared to the chemical immobilization method, the physically immobilized PMMP complex achieved a higher capture efficiency initially, with excellent selectivity towards target bacteria. The PMMPs were further tested for selective isolation of L. monocytogenes using real food samples such as ground beef and whole milk.

SIFAT MAGNETIK DAN UKURAN PARTIKEL MAGNETIK SERTA KOMPOSISI MATERIAL PASIR BESI PANTAI KATA PARIAMAN SUMATERA BARAT DI SINTESA DENGAN IRON SAND SEPARATOR DAN BALL MILLING

Research on influence of Ball Milling time on magnetic properties composition and particle size of iron sand has been studied by Iron Sand Separator. The sampel was collected Kata beach Pariaman West Sumatera. Magnetic properties was studied using a solenoid wound with 2000 turns, length of 10 cm, and diameter 3 cm. Composition of the sample was studied by X-Ray Fluorescence, while particle size of the sample was studied by Particle Size Analyzer. The results showed that the size particle is 99,14 μm, 96,59 μm, and 93,34μm after processing by Ball Milling of 3, 5, and 7 hours respectively. The composition of the sample after being processed by Ball Milling of 7 hours is 12,2% and 47,387% respectively. More over, mass suseptibility of the sample increased after being processed by Ball Milling from 873,62 x 10-8 m3/Kg to 14.576,52 x 10-8 m3/Kg. These values are interval of ilmenite mineral (46 x 10-8 – 80.000 x 10-8) m3/Kg.

MAGNETIC AND THERMAL PROPERTIES OF NANOMATERIALS BASED ON HIGHLY BRANCHED FERROCENE-CONTAINING POLYMERS

New magnetic nanomaterials with magnetization up to 32 Gs·cm3/g were synthesized from highly branched ferrocene-containing polymers by thermal structural transformations in a field of 2.5 kOe. The structure and properties of the prepared polymers were studied by IR spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analyses. According to IR spectroscopy the content of 1,3,5-substituted benzene rings in the ferrocene-containing polymer increases at 500°C. X-ray diffraction study showed that iron in such a sample is present exclusively in the form of Fe3O4 magnetite. As the heating temperature increased to 600°C, the composition of the samples became more complex: along with magnetite they contain cementite Fe3C and wustite FeO.97O. The magnetization of the ferrocene-containing polymer depends on the synthesis and heat treatment temperature. For a sample synthesized at 140°C the formation of a magnetically ordered phase begins at 500°C, and at 800°C the magnetization reaches a maximum value of 32 Gs·cm3/g. The average size of magnetic particles according to TEM analysis was 8-26 nm. The principal possibility of controlling the size and composition of the nanoparticles, as well as their magnetization depending on the conditions of production and the temperature of polymer structuring is shown. The obtained results provide a good basis for the directed synthesis of magnetic ferrocene-containing polymers with preset characteristics.

Hyperthermia System Based on Extrinsically Magnetic Poly (Butylene Succinate)

In this work, an extrinsically magnetic composite based on modified magnetite and poly (butylene succinate) (PBS) is prepared. The magnetic composite is obtained by the emulsion–solvent evaporation method. Several analytical tests confirm the synthesis of the composites. Among them, Nuclear magnetic resonance (NMR) results in comparison with literature confirms the synthesis of PBS. X‐Ray Diffraction (XRD) shows the characteristic peaks of PBS, in its monoclinic structure. The crystallite size (Lc) of magnetic particles inside the composite, is equal to 13 nm. Thermogravimetric analysis (TGA) reveals the presence of 5.3 wt% magnetite in the composite and demonstrates that the inclusion of magnetite does not affect the thermal stability of the polymer. The analysis of Fourier transform infrared attenuated total reflection spectra (FTIR‐ATR) indicates the synthesis of desired products as well as the encapsulation of magnetite in PBS polymer matrix. The composite presents magnetic force, which allows its magnetic guidance to a target area. Besides, the magnetic induction heating test promotes heating within the therapeutic range from 40 to 45 °C, being able, according to literature, to promote the death of several types of cancer's cells. Therefore, the material here presented possesses potential to be deeply researched as a future cancer treatment tool.

Magnetic tracing of sediment dynamics of mudbanks off southwest coast of India

In this study, we utilized environmental magnetic in combination with sedimentological and hydrodynamic data to investigate the formative processes of mudbanks along southwest coast of India. We document the linkages between enrichment of silt-sized magnetic particles and formation processes of mudbanks along Alappuzha coast. A trend of increasing magnetite concentration and coarsening in magnetic grain size is observed at mudbank stations M2 and M3, while the mud-deficient station (M1) showed an opposite trend. A strong relationship between magnetic and physical grain size for all samples implies that the magnetic particle size and clastic grain size are largely adjunct. Analysis of rock magnetic and grain size data of surficial and suspended sediments from non-mudbank (M1) and two mudbank stations (M2, M3) reflect the differential sediment partitioning and transport regimes which controlled the formation of mudbanks along Alappuzha coast. Two plausible mechanisms responsible for the formation of mudbanks are identified: grain size-selective entrainment is the dominant process during pre-monsoon; weaker hydrodynamics (waves and bottom currents) favors accumulation of silt-sized (fine and coarse) magnetic and non-magnetic fractions resulting in the formation of magnetically low-enriched sediment bed of mixed grain sizes. At the onset of monsoon, wave-induced energetic bottom currents enhance the suspension of entire sediment bedload at stations M2, M3 to form fluid mud. Concurrently, mineral-density-based selective fractionation allows the settling of coarse silt-sized magnetic particles, while the fine magnetic silt-size particles accumulate forming thick fluid mud as a suspension load resulting in the formation of mudbanks. An observed increase in magnetic susceptibility and coarsening in magnetic grain size of surficial sediments at mudbank stations (M2, M3) during monsoon period supports the interpretation. Our findings are summarized in a conceptual model which can be very well applied to investigate sediment dynamics associated with mudbank formation in coastal and shelf sedimentary systems.

3D-printed microfluidic manipulation device integrated with magnetic array

This paper reported a transparent, high-precision 3D-printed microfluidic device integrated with magnet array for magnetic manipulation. A reserved groove in the device can well constrain the Halbach array or conventional alternating array. Numerical simulations and experimental data indicate that the magnetic flux density ranges from 30 to 400 mT and its gradient is about 0.2–0.4 T/m in the manipulation channel. The magnetic field parameters of Halbach array in the same location are better than the other array. Diamagnetic polystyrene beads experience a repulsive force and move away from the magnetic field source under the effect of negative magnetophoresis. It is undeniable that as the flow rate increases, the ability of Halbach array to screen particle sizes decreases. Even so, it has a good particle size discrimination at a volumetric flow rate of 1.08 mL/h, which is much larger than that of a conventional PDMS device with a single magnet. The observed particle trajectories also confirm these statements. The deflection angle is related to the magnetic field, flow rate, and particle size. This 3D-printed device integrated with Halbach array offers excellent magnetic manipulation performance.

High‐resolution paleoclimatic records spanning the past 30 cal ka BP inferred from Qionghai Lake sediments in south‐west China: Insights from geochemical investigations and grain‐size characteristics

There have been few high‐resolution investigations covering the last glacial and Holocene from Sichuan, Yunnan, or south Asia area in the south‐west monsoon domain region. High‐resolution analyses of lake sediments retrieved from Qionghai Lake, Sichuan Province, were conducted using a combination of variables including total organic carbon (TOC) and total nitrogen (TN) concentration, low frequency magnetic susceptibility (χLF), particle size, carbonate content, and δ13C value of organic matter (δ13Corg), to provide a new perspective on the detailed paleoclimate history of south‐west China spanning the past 30 cal ka BP. Our findings suggest that organic matter in the Qionghai Lake was mainly derived from microorganisms, aquatic macrophytes, and terrestrial C3 plants. From 29.1 to 23.2 cal ka BP, low carbonate contents, high median grain size (Md values), and χLF values indicated a warm and wet climate. During the period 23.2 to 15.4 cal ka BP, low χLF, Md values, and high carbonate contents suggested a decrease in temperature and humidity. The cold and dry Last Glacial Maximum (LGM) and Heinrich 1 event (H1) were captured between 21.6 and 19.4 cal ka BP and 17.6 and 15.8 cal ka BP, respectively. During the interval 15.4 to 9.7 cal ka BP, low level of χLF values and Md values, together with relatively high carbonates, demonstrated that a dry climate prevailed in this period. Since 9.7 cal ka BP, the climate was warm and humid in the early to mid‐Holocene and shifted towards cold and dry condition in the late Holocene. A cold and dry period at 8.5 to 8.1 cal ka BP and warm and wet interval at 6.6 to 4.6 cal ka BP were identified, corresponding to the 8.2‐ka cold event and Holocene climatic optimum (HCO), respectively. These climate changes may reflect variations of the intensity of the south‐west summer monsoon, primarily in response to the Northern Hemisphere solar insolation on a millennial scale induced by orbital forcing. The position of the Intertropical Convergence Zone (ITCZ) may add a complementary effect on the evolution of the monsoon strength in the Holocene.

Effects of surfactant on the structural and magnetic properties of hydrothermally synthesized NiFe2O4 nanoparticles

A simple and effective hydrothermal route is adopted where glycerol and NaOH are used as surfactant and precipitating agents respectively, for the synthesis of NiFe2O4 (NFO) magnetic nanoparticles. The structure and morphology of the as prepared NFO are characterized by X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) techniques. The formation of phase-pure NFO is evident from the XRD studies. The crystallite size calculated using the Scherer equation are in the range of 22–38 nm. A mixed morphology of spherical and octahedral shape are found in FESEM images depending on the concentrations of glycerol as surfactant. The increase in Curie temperature (Tc) from 805 to 815 K is observed, when the surfactant concentration is increased from 10 to 20% w/v. However with an increase in surfactant concentration to 40% w/v, the Tc decreases to 790 K. The NFO nanoparticles prepared at 10% w/v surfactant concentration show a high saturation magnetization (Ms) of 42 emu/g which increases to 53 emu/g at 20% w/v of surfactant. Very small change in Ms (decrease of 1–2 emu/g) is noticed with further increase in surfactant to 40% w/v. The possible explanations are hypothesized for such observed phenomena. A linear dependence of coercivity (Hc) and remanence (Mr) with surfactant concentrations is found for NFO nanoparticles, where both Hc and Mr decrease with increase in surfactant concentrations. It is found that glycerol, which is economical and eco-friendly, is an effective surfactant to prepare NFO nanoparticles with desirable magnetic properties and controllable particle size.

Simulation of water purification using magnetically ultra-responsive micro- and nanoscavengers

Access to clean water is one of the challenges of the 21st century. Thus water purification is inevitable. One method of water treatment is purification by magnetic particles in the presence of magnetic field. The contaminants are attached to the magnetic particles and then by applying a magnetic field, magnetic particles and, thus, the pollutants can be collected. For the optimal design of a water treatment system, the effect of important parameters in the design, such as magnetic fields, particle size, and Reynolds number are determined numerically by modeling and simulating the water treatment process. Two methods are used to create the magnetic field: permanent magnet and coils. It is shown that there is very little difference in the collection efficiency. Particle size is varied from micrometers to nanometers. In general, the collection efficiency increases by increasing the particle diameter and decreasing the Reynolds number. For example, it is shown that with a magnetic field of strength 0.05 T and Reynolds number of 100, particles with a diameter of 30 micrometers and above are collected completely. However, with decreasing particle diameter to the nanometer, collection efficiency finds a sharp drop. Using baffles to shift the particles toward regions with stronger fields, it is possible to increase the collection efficiency for nanoparticles.

Tunable Curie temperature of Mn0.6Zn0.4Fe2O4 nanoparticles

Synthesis of stable temperature sensitive magnetic fluids that can be used in heat exchange devices having desired magnetic properties and tunable Curie temperature is quite challenging as their performance parameters are strongly correlated with preparation conditions of magnetic nanoparticles. In this article, we report size dependence of Curie temperature and saturation magnetization of Mn0.6Zn0.4Fe2O4 (MZ4) nanoparticles synthesized by co-precipitation method by controlling the pH, reaction temperature and reaction time. As-synthesized MZ4 nanoparticles have tunable Curie temperature that ranges between 392 K and 665 K. These magnetic nanoparticles are well suited for cooling applications in energy conversion electronic devices as their Curie temperatures are close to the working temperature of these devices. The observed tunability of Curie temperature and magnetization of MZ4 nanoparticles are analysed in terms of the corresponding changes in the magnetic particle size and distribution of Mn ions between tetrahedral (A-site) and octahedral (B-site) in an inverse spinel structure.

High magnetization Co-GdOx superparamagnetic granular films as magnetic coating materials for high-sensitivity alternating magnetic force microscopy tip

The Coy(GdOx)1−y, CoyAg1−y, (Fe70Co30)y(AlOx)1−y superparamagnetic (SP) granular films were fabricated by magnetron co-sputtering technique and compared for their magnetic properties. The effect of the different matrix (GdOx, Ag, AlOx) is investigated for refining and separating magnetic particles in non-magnetic matrix by calculating the magnetic volume fraction (y), and the results indicate that the GdOx matrix can more effectively refine and separate magnetic particles. The Co0.44(GdOx)0.56 SP film with the maximum Co volume fraction (y = 0.44) approaches the highest magnetization of 608 emu/cm3 at 20 kOe, and initial susceptibility (1.74 × 10−5 H/m) as compared with Co-Ag, Fe70Co30-AlOx films and some systems of other researchers at room temperature (RT). The magnetic particle size and size distribution in these SP films is calculated by fitting with Langevin function and the results of calculation are consistent with the high-resolution transmission electron microscopy (HRTEM) results. To further confirm the SP behavior, the blocking temperature of the Co0.44(GdOx)0.56 film with the maximum Co volume fraction is measured as ∼145 K, which is below RT. Finally, the Co0.33(GdOx)0.67 thin film having a linear magnetization curve is used for the fabrication of the SP tip and further used for the A-MFM measurement on the bulk Sr-Ferrite (SrF) magnet. The fabricated Co0.33(GdOx)0.67 SP tip along with A-MFM shows an excellent result as compared to the state of art FePt hard magnetic tip using conventional MFM, and it can directly detect the intensity and identify the polarity of the stray field originating from a bulk Sr-Ferrite (SrF) permanent magnet without topography crosstalk in ambient atmosphere.

Paleomagnetic results from Lower Devonian sandstones of the Niqiuhe Formation in the Duobaoshan area and its constraints on paleoposition of the Xing’an block

Two common but contradictory views toward the timing of the final closure of the eastern Paleo-Asian Ocean (PAO) are either the Pre-Late Devonian or the Late Permian to Early Triassic. Previous paleomagnetic studies support a consolidation of the unified North China and Mongolia by the Late Permian. However, Pre-Late Permian paleogeography of the eastern Central Asian Orogenic Belt (CAOB) is not well understood due to the scarcity of reliable paleomagnetic records. The Xing’an block plays a key role in the evolution of the CAOB, however, no paleomagnetic results are available so far to provide constraints on its Late Paleozoic paleo-position. We performed a systematic paleomagnetic study on a purple siltstone section of the Lower Devonian Niqiuhe Formation near the Duobaoshan County, Heilongjiang Province. Representative fresh end samples were subjected to rock magnetic analysis to identify their dominant magnetic carriers and particle size distribution. Rock magnetic experiments include measurements of magnetic susceptibility variation dependence of temperature ( κ - T ) curves, hysteresis loops, acquisition of isothermal remanent magnetization (IRM) and back-field demagnetization of saturated IRM (SIRM) curves. The results indicate that the magnetic remanence carriers are dominant by hematite with minor contributions of magnetite. 112 cylindrical specimens were thermally demagnetized using an ASC TD-48S furnace and measured in a 2G-755-4K SQUID system in the Magnetotectonics Lab of Peking University. A total of 11 sites revealed identical bi-components character. The low temperature component resembles the present geomagnetic field in geographic coordinates, while the high temperature characteristic remanence (ChRM) component was reversed polarity both before and after tilt correction. Optimal concentration is achieved at 35.7% unfolding percentage, which suggests the magnetization was acquired during the late stage of a folding process. A previous structural study indicated that stress field of the research area switched from NW-SE to N-S orientation during the Late Permian, which is supported by the predominant NE-SW oriented Ordovician to Devonian strata as well as the angular unconformity between the Devonian and Upper Permian strata. The folding time of the Niqiuhe Formation is likely Middle Devonian to Middle Permian. Supported by evidence from a suite of granites near our sampling section (less than 3 km) dating at 309−299 Ma along with the universal reversed polarity of all 11 sites, we argue that the ChRM component was acquired during the Permo-Carboniferous Reversed Superchron (~318−262 Ma), when the study area was affected by a granitic intrusion thermal event (309−299 Ma). The ChRM component ( D / I =28.6°/−33.2°, k =18.6, α 95=10.9°) corresponds to a paleomagnetic pole of λ p/ φ p=17.3°S/97.1°E ( dp / dm =7.0°/12.4°). For a common reference site (43°N/114°E), our results suggest the Xing’an block was situated at 27.7°±12.4°N during the Late Carboniferous. Coeval results obtained from rocks of different lithology suggest 28.5°±9.7°N and 19.9°±14.8°N for the Uliastai continental margin and the Central Mongolia-Euruna block. After applying a blanket flattening factor f =0.6 for results obtained from clastic sedimentary rocks, the paleolatitudinal difference between the Xing’an block, Uliastai continental margin, and the Central Mongolia-Erguna block is less than 3.2°±12.8°. Late Carboniferous paleomagnetic poles from those three blocks are distributed along a small circle. Significant post-Permian local rotations are likely attributed to extensive Mesozoic strike-slip faults among the eastern CAOB. Those three blocks were probably consolidated into a unified block, situated at ~28°−30°N during the Late Carboniferous and dominant by the cold water Borel realm fauna. By contrast, the North China and Songliao-Xilinhot blocks was situated at an equatorial region (4.3°S−12°N) and dominant by the warm water Tethyan realm fauna, while Siberia was located at ~45°−50°N. The Paleo-Asian Ocean therefore remained open and the main basin was the Hegenshan ocean rather than the Solonker ocean.

STUDI SIFAT MAGNETIK DAN UKURAN PARTIKEL ABU VULKANIK ERUPSI GUNUNG SINABUNG KABUPATEN KARO MENGGUNAKAN PROBE PASCO 2162

This study aims to determine the magnetic properties and particle size of the volcanic ash of Sinabung Mount with experiment method. Magnetic properties studied were magnetic degree, magnetic induction magnetic susceptibility, and mass susceptibility of sample. The samples used were volcanic ash taken from the west part of Sinabung, precisely at Gurukinayan village. The ash samples were taken horizontally on the slopes of the Mountain with the amount of 1.5 Kg each point with the number of 10 points (A to J). Separation of concentrate of ash was done using a Neodymium Iron Boron (NdFeB). The magnetic induction of ash and concentrate was measured using a Pasco 2162 Probe using a solenoid is 3 cm in diameter, 10 cm in length and 2000 coil turns. Magnetic induction without a core was measured as a current function (2,4,6,8,10)A and a distance of 1 to 5 mm. The total magnetic induction of ash and concentrate was measured as a current function and the particle sizes was measured using a Light Microscope. The results showed that the greate magnetic degree value at point B of 7.02% and the lowerst level of magnetism is at point J was 1.07%. The largest particle sizes is at point B and the smallest is at point J with particle size of 0.175-0.90 mm. The highest average magnetic susceptibility value for concentrate at point B is 87.32 x 10-3 and the lowest at point F is 20 x 10-3. Based on the mass susceptibility value of the concentrate obtained the volcanic ash of Mount Sinabung is at interval (46–80.000) x 10-8 m3/kg of mass susceptibility value at each location point which contains Ilmenite particles (FeTiO3).

Modelling study on the three-dimensional neutron depolarisation response of the evolving ferrite particle size distribution during the austenite–ferrite phase transformation in steels

The magnetic configuration of a ferromagnetic system with mono-disperse and poly-disperse distribution of magnetic particles with inter-particle interactions has been computed. The analysis is general in nature and applies to all systems containing magnetically interacting particles in a non-magnetic matrix, but has been applied to steel microstructures, consisting of a paramagnetic austenite phase and a ferromagnetic ferrite phase, as formed during the austenite-to-ferrite phase transformation in low-alloyed steels. The characteristics of the computational microstructures are linked to the correlation function and determinant of depolarisation matrix, which can be experimentally obtained in three-dimensional neutron depolarisation (3DND). By tuning the parameters in the model used to generate the microstructure, we studied the effect of the (magnetic) particle size distribution on the 3DND parameters. It is found that the magnetic particle size derived from 3DND data matches the microstructural grain size over a wide range of volume fractions and grain size distributions. A relationship between the correlation function and the relative width of the particle size distribution was proposed to accurately account for the width of the size distribution. This evaluation shows that 3DND experiments can provide unique in situ information on the austenite-to-ferrite phase transformation in steels.