Concentration Of Magnetic Particles Research Articles

Magnetic withdrawal of particles for multiple purposes in nuclear power plants

Several parametric effects on the magnetic collection have been evaluated considering dimension, strength of external magnetic field, injected velocity and particle concentration in the working fluid. Besides, accidental environments, expected in the containment of nuclear power plants, have also been addressed for the capture efficiency. The capture efficiency is especially enhanced with magnetic particle size and magnetic field strength through increased magnetic force; the non-magnetic coating thickness and fluid velocity hinder the magnetic collection. Based on the assessment, the magnetic withdrawal system can effectively capture magnetic particles even under accidental environments. Withdrawal of multifunctional magnetic particles or filtering of magnetic impurities can be effectively realized through the system.

ИССЛЕДОВАНИЕ ГЕРМЕТИЗИРУЮЩЕЙ СПОСОБНОСТИ КОМБИНИРОВАННОГО МАГНИТОЖИДКОСТНОГО УПЛОТНЕНИЯ ПОДШИПНИКОВЫХ УЗЛОВ

The purpose of the research is to increase the efficiency of hermetic ability of bearing assemblies by using com-bined ferrofluidic sealed. The research objective is theoretic justification of the maximum concentration of ferro-magnetic particles in fluid, investigation of hermatic ability of a combined ferrofluidic seal under conditions of tem-perature changing and speed of a shaft rotation of packing bearing assembly. The study of hermetic ability of lip and ferro-fluidic sealed was carried out on a test bench, allowing to determine the packing ability of seals both in static and dynamic mode. On the basis of theoretical data, formulas were determined to find the maximum concen-tration of hard and magnetic phases in a ferrofluid, and its composition based on a polyethylsiloxane liquid PES-5 with a 40 kA/m saturation magnetization and a 1.2 Pas dynamic viscosity coefficient was developed. A mixture of magnetite with powdered iron was used as the ferromagnetic phase. Oleic acid was used as a surfactant. Studies to determine hermetic capacity have shown a higher efficiency of the combined ferrofluidic seal compared to the lip one. During static test within the temperature range between 20 to 600C, the critical pressure difference of the com-bined seal was 
 4-16% higher than that of the lip seal. Temperature increase of the bearing assembly from 20 to 1200C causes a decrease in critical pressure difference of up to 50%. This is due to a decrease in the sedimentative stability of the magnetic fluid as a result of an increase in temperature. Studies show that the combined ferrofluidic seal has a higher hermetic tightness at the starting torque than the standard lip seal. In contrast to the lip seal (which tends to lose its tightness at the starting torque), no leakage of pressure fluid from the sealed unit was observed of the com-bined ferrofluidic one with a pressure drop of 0.094 MPa. The results obtained allow reasonably select the concen-tration of magnetic particles in the ferrofluid, and also prove the prospects of replacing standard lip seals with com-bined ferrofluidic ones.

Dietary Strawberries Improve Cardiometabolic Risks in Adults with Obesity and Elevated Serum LDL Cholesterol in a Randomized Controlled Crossover Trial.

Background and aims: Dietary berries, such as strawberries, are rich in bioactive compounds and have been shown to lower cardiometabolic risk. We examined the effects of two dietary achievable doses of strawberries on glycemic control and lipid profiles in obese adults with elevated serum LDL cholesterol (LDL-C). Methods: In this 14-week randomized controlled crossover study, participants were assigned to one of the three arms for four weeks separated by a one-week washout period: control powder, one serving (low dose: 13 g strawberry powder/day), or two-and-a -half servings (high dose: 32 g strawberry powder/day). Participants were instructed to follow their usual diet and lifestyle while refraining from consuming other berries and related products throughout the study interval. Blood samples, anthropometric measures, blood pressure, and dietary and physical activity data were collected at baseline and at the end of each four-week phase of intervention. Results: In total, 33 participants completed all three phases of the trial [(mean ± SD): Age: 53 ± 13 y; BMI: 33 ± 3.0 kg/m2). Findings revealed significant reductions in fasting insulin (p = 0.0002) and homeostatic model of assessment of insulin resistance (p = 0.0003) following the high dose strawberry phase when compared to the low dose strawberry and control phases. Glucose and conventional lipid profiles did not differ among the phases. Nuclear magnetic resonance-determined particle concentrations of total VLDL and chylomicrons, small VLDL, and total and small LDL were significantly decreased after the high dose strawberry phase, compared to control and low dose phases (all p < 0.0001). Among the biomarkers of inflammation and adipokines measured, only serum PAI-1 showed a decrease after the high dose strawberry phase (p = 0.002). Conclusions: These data suggest that consuming strawberries at two-and-a-half servings for four weeks significantly improves insulin resistance, lipid particle profiles, and serum PAI-1 in obese adults with elevated serum LDL-C.

Magnetic Biomonitoring Using Native Lichens: Spatial Distribution of Traffic-Derived Particles

Air pollution has become a subject of extensive study of several disciplines and it is identified as one of the most damaging factors for the ecosystem and human health. In urban areas, particle emission can be found in suspension and therefore a portion of them is inhalable for humans, or deposited on streets and several surfaces, including lichen’s thallus. We studied particulate matter (PM) (by traffic emission) accumulated in native lichens Parmotrema pilosum in order to carry out a magnetic biomonitoring over 2016 and 2017. For this purpose, the environmental magnetism method was complemented with inductively coupled plasma optical emission spectrometry, scanning electron microscopy, and geostatistical methods. The accumulated iron oxides on lichen’s thallus include potential toxic elements, such as Ba, Cr, Ni, and V. Fe-rich particles related to vehicle emissions correspond to (ultra)fine magnetite of inhalable sizes (PM2.5). Our results indicate a relation between concentration of magnetic particles and areas with high traffic, as well as the influence of rainfall on magnetic PM records. Magnetic biomonitoring is validated as a low-cost and complementary methodology to determine levels of air magnetic PM pollution in cities.

Bursera fagaroides bark as a bioindicator for air particle pollution using magnetic properties

Shrub barks can accumulate airborne particles and seem to be suitable biological monitors for assessing air pollution. We studied the bark of the species Bursera fagaroides as a biomonitor of air pollution in an urban area of Mexico. Samples were collected in dry and rainy seasons during 2011 and 2012, in 28 sites which are exposed to magnetic pollutants emitted by different human activities (industrial point-sources and vehicular emissions). Environmental magnetism studies allow determining mineralogy, concentration and grain size of magnetic particles accumulated in barks, providing information on the sources and characteristics of their emitted particles. Magnetic properties of all samples were determined by environmental magnetism method. The highest values of magnetic concentration dependent parameters were observed in industrial and vehicular traffic sites. The mean values of saturation of isothermal remanent magnetization SIRM for dry seasons are two to threefold (SIRM = 0.8–1.2 × 10−3Am2kg−1) the mean value for rainy season (SIRM = 0.4 × 10−3Am2kg−1). The integrated magnetic analysis indicates the presence of ferrimagnetic minerals, mostly magnetite-like (remanent coercivity Hcr = 31.6–38.7 mT) particles of small sizes (1 – < 0.1 μm). Selected samples were observed by scanning electron microscopy, revealing the presence of such iron-rich particles hosted in species’ lenticels. These results demonstrate the usefulness of the species' cortex as a biomonitor of air pollution, with an affordable and immediate application, and raise new questions about what type of physiological mechanism is involved for trapping magnetic particles.

An innovative magnetic bar separator for removal of chromium ions in tanning wastewater

An innovative magnetic separator was designed to capture chromium ions in tanning wastewater through magnetic nanoparticles. The effect of Fe3O4 magnetic particle concentrations, magnetic bar spacing and liquid flow velocities on the capture efficiency of the magnetic separator on magnetic nanoparticles in a simulated system was investigated. When the concentration of the magnetic particles is less than 400mg/L, the flow velocity is lower than 18L/hr, and the spacing of the magnetic bar is less than 30mm, the capture efficiency of Fe3O4 magnetic nanoparticles could keep more than 99.4 % within 3h. The magnetic separator was applied to treat chromium-containing tanning wastewater. The initial chromium concentration of the wastewater is 127mg/L. The capture efficiency could keep 99.7 % during 5 h, the wastewater treatment capacity is 18 L/hr and the outlet Cr<0.5mg/L. Amino Fe3O4 can be regenerated and reused 9 times, the chromium capture rate is above 99.6 %, and the outlet Cr<0.5mg/L. The magnetic separator is suitable for large-scale heavy metal wastewater treatment.

Three-dimensional model of magnetic susceptibility in forest topsoil: An indirect method to discriminate contaminant migration.

Soil magnetic susceptibility (MS) is an important parameter in pollution studies owing to its relationship with atmospheric deposition, and the concomitance of technogenic magnetic particles (TMPs) with potentially toxic elements (PTEs), Fe and Mn. In this study, we performed a detailed soil study under tree canopies for a forest area with high historical TMP-bearing industrial dust deposition. The technogenic sources of magnetic signals in topsoil were analyzed via scanning electron microscope electron dispersive spectroscopy (SEM/EDS), while the minor role of geogenic sources was obtained from soil profile analysis. To our knowledge, this is the first study to show soil TMP distribution in three dimensional (3D) space. In addition, using the data from 275 soil cores and 8250 individual measurements, 3D maps of MS for four tree species were plotted. There is a noticeable difference between coniferous (spruce and pine) and deciduous (beech and oak) species regarding depth of maximum concentration of magnetic particles in the topsoil. For beech and oak, maximum MS values were measured at 3cm depth; pine and spruce, maximum MS values were measured at 5cm depth. However, no significant differences were found among tree species in terms of mean MS or PTE contents. This suggests that there is little different among tree species in terms of dust capture over their life span. Significant correlations between MS and other parameters (PTEs and organic matter contents) present new possibilities for spatial 3D analysis of topsoil horizons.

Prolific shedding of magnetite nanoparticles from banknote surfaces

Here, we use magnetic methods first to quantify the content of strongly magnetic particles of banknotes (US dollars, USD, and British pounds sterling, GBP), and then examine the possibility of their release from handled banknote surfaces. The content of magnetic particles, from magnetic remanence measurements, for the USD and paper GBP banknotes is high; greater, for example, than that in vehicle engine-exhaust emissions, and similar to that for airborne roadside particulate matter (PM). Our magnetic analyses of USD and GBP banknotes, and of the ink pigment widely used in their printing, reveal not only that the banknotes are highly magnetic, but also that strongly magnetic, nano-sized particles are readily and prolifically shed from their surfaces (especially from the USD banknotes). A common practice, prior to increased automation, was for bank tellers to count banknotes by licking a finger to adhere to each successive counted note, and thus speed up the manual counting process. Given the rate of particle shedding reported here, this traditional manual counting procedure must have resulted in prolific transfer of iron-rich nanoparticles both to the fingers and thence to the tongue. We hypothesise that, pre-automation, magnetite and other metal-bearing nanoparticles were repetitively and frequently ingested by bank tellers, and subsequently entered the brain directly via the taste nerve pathway, and/or indirectly via the systemic circulation and the neuroenteric system. This hypothesis may plausibly account for the reported and currently unexplained association between elevated neurodegeneration-related mortality odds ratios and this specific occupation.

Magnetic particles in the sediments of the south Ukraine rivers as the marker of the technogenic impact on the hydroecosystems

Long-term and large-scale man-made activity in the mining areas affects to all components of the biosphere. The result of mining impact on hydroecosystems is addition to natural sources of sedimentary material technogenic components in large volumes. Magnetic particles are one of technogenic components which come with surface run-off to the river bed. We have studied the content of magnetic particles in the sediments of the south Ukraine rivers: the Inhulets River and the Inhul River ‒ the tributaries of the Dnieper and the Southern Buh, respectively. The Inhulets River flows along the Kryvyi Rih iron ore deposit, parallel the river there is a chain of open-pits, mines, mining and processing plants, a metallurgical plant. The results of our research were demonstrated within the Kryvyi Rih industrial agglomeration a number of magnetic particles in the sediment samples varies from 59,5% to 2,1%. Upstream from the Kryvyi Rih city on 10-15 km a number of magnetic particles is within 1,5%. Based on numerous sources of literature and own researches, it has been determined that detection of magnetic particles and properties is a convenient, cheap, quick and informative method of technogenic pollution studying of river sediments and also mirror the industrial history of the region.

Analysis of magnetorheological grease normal force characteristics in static and dynamic shear modes

In this paper, the normal stress behavior of magnetorheological grease (MRG) in a quiescent state and its dynamic shear modes were systematically studied. Three types of magnetorheological greases were prepared, MRG-30, MRG-50, and MRG-70 with 30%, 50%, and 70% carbonyl iron(CI) powder mass, respectively. Furthermore, static and dynamic shear tests were carried out using a rheometer, the effects of time, magnetic field strength, shear rate and temperature on normal stress were studied and analyzed under both static and dynamic conditions. In the static mode, the research results show that the normal force is related to the magnetic field strength and the content of magnetic particles in the MR grease, but has nothing to do with historical time. the static normal stress generates the evident fluctuation with changing the temperature when magnetic field strengths of 96 kA m−1 and 194 kA m−1. The fluctuation is very small when the magnetic field strengths are 0kA m−1, 391 kA m−1 and 740kA m−1. Similar to the static normal stress, the dynamic normal stress at the degaussing is greater than the normal stress during magnetic field loading. The dynamic normal stress are almost invariant with prolonging the time below 100 s−1 shear rate under the medium magnetic field strength of 194 kA m−1 whereas the stress is increased at the shear rate of 100 s−1. Besides, the dynamic normal stress is basically independent from the time above the shear rate 0f 1 s-1 at the high magnetic field of 740 kA m−1. Under other conditions, the normal force basically presents a stable value. At the absence of the magnetic field, there are quietly weak effects of temperature on the static and dynamic normal stress. Finally, when a magnetic field strength higher than 96 kA m−1 is applied to the material, the value of dynamic normal stress increases with temperature.

Model-based optimized steering and focusing of local magnetic particle concentrations for targeted drug delivery

Magnetic drug targeting (MDT) is an application in the field of targeted drug delivery in which magnetic (nano)particles act as drug carriers. The particles can be steered toward specific regions in the human body by adapting the currents of external (electro)magnets. Accurate models of particle movement and control algorithms for the electromagnet currents are two of the many requirements to ensure effective drug targeting. In this work, a control approach for the currents is presented, based on an underlying physical model that describes the dynamics of particles in a liquid in terms of their concentration in each point in space. Using this model, the control algorithm determines the currents generating the magnetic fields that maximize the particle concentration in spots of interest over a period of time. Such an approach is computationally only feasible thanks to our innovative combination of model order reduction with the method of direct multiple shooting. Simulation results of an in-vitro targeting setup demonstrated that a particle collection can be successfully guided toward the targeted spot with limited dispersion through a surrounding liquid. As now present and future particle behavior can be taken into account, and non-stationary surrounding liquids can be dealt with, a more precise and flexible targeting is achieved compared to existing MDT methods. This proves that the presented methodology can bring MDT closer to its clinical application. Moreover, the developed model is compatible with state-of-the-art imaging methods, paving the way for theranostic platforms that combine both therapy as well as diagnostics.

Magnetic solid phase extraction of silver-based nanoparticles in aqueous samples: Influence of particle composition and matrix effects on its application to environmental samples and species-selective elution and determination of silver sulphide nanoparticles with sp-ICP-MS

Silver-based nanoparticles (Ag-b-NPs) are currently a cause for concern because they are being produced in increasing quantities for use in industrial goods and consumer products. This goes hand in hand with their release to the environment and the resultant risks for the entire ecosystem. Therefore, it is essential that these materials are monitored. A promising technique that overcomes a number of shortcomings in handling environmental samples is magnetic solid phase extraction (MSPE) of Ag-b-NPs, which is applied in this study. It has been possible to extract different kinds of Ag-b-NPs at environmentally relevant concentrations in the low ng L−1 range using iron oxide magnetic particles (IOMPs) of different size and shape with efficiencies in the range from 80 to 100%. Furthermore, environmentally relevant inorganic ions and TiO2 particles exhibited no major effect on the extraction efficiency. However, natural organic matter (NOM) exhibited a significant influence from 1 mg L−1 resulting in a 50% drop in extraction efficiency. This effect could be overcome by adding 10 mM Ca2+ or increasing the iron oxide magnetic particle (IOMP) concentration to 500 mg L−1. Applying the presented procedure, Ag-b-NPs added to a river water sample at βAg = 50 ng L−1 were successfully extracted. We also investigated the coextraction of Ag+, demonstrating that NOM could eliminate coextraction. The subsequent species-selective elution of Ag2S-NPs after MSPE, was carried out based on ethylene diamine tetraacetate (EDTA) as eluent in different matrices. A desorption efficiency of 76 ± 6% could be achieved while preserving the Ag2S-NPs' size. By contrast, core Ag-NPs and AgCl-NPs are dissolved if the presented method is followed.

Magnetorheological cements for plug setting control in oil and gas wells

Magnetorheological-blended cements (MRBC) are promising materials for plugging and abandonment applications in oil and gas wells because their viscosity can be reversibly controlled through the addition of magnetic particles and application of an external magnetic field. In this study, the fresh state and hardened state properties of MRBC with varied amounts of additives were investigated, including fresh slurry viscosity, thickening time, and compressive strength. A new test method was developed to determine the pressure a liquid MRBC column can hold while activated by a magnetic field. Results showed that the apparent viscosity of MRBC formulations increased as the content of magnetic particles increased, while thickening time was reduced. Compressive strengths of MRBC were found to be similar to standard neat slurries, with MRBC showing slightly higher early strength. The newly developed pressure testing method demonstrated that the MRBC fluid columns tested were able to hold more than the minimum goal of 345 kPa (50 psi) of pressure before movement was indicated. This MRBC characteristic can be exploited to form temporary and permanent cement barriers both inside casing and open hole, as well as in casing annuli. For the latter application, it was shown that sufficient magnetic field strength (in the range of 0.15T–0.25T) can be generated in the annular space outside of a stainless steel casing with the magnet located inside the casing, to still effectively magnetize the MRBC slurry.

The study on the mechanical properties of magnetorheological elastomers under triaxial compression

In order to design magnetorheological elastomers (MREs) based craftsmanship for metal forming, a comprehensive study on the mechanical properties of MREs under triaxial compression is required. An experimental setup integrating free compression and triaxial compression is designed to characterize isotropic MREs specimens under compression mode. The results showed that the MREs specimen in mold had successively experienced free compression stage, transition stage and triaxial compression stage during the experiment. The stress-strain curves of the MREs specimen changed when the concentration of magnetic particles increased from 0 to 44.7%, and the strain required to reach the transition stage was reduced. The effect of magnetic flux density on the stress-strain curves of the MREs specimen depended on the concentration of magnetic particles. The measured data obtained at different strain rates revealed maximum changes of 15.7% and 0.096% in volume compression modulus and Poisson ratio, respectively, which occurred under the magnetic flux density of 200 mT and CIP concentrations of [Formula: see text]. In this study, through a set of experiments, the stress-strain curves of the MREs specimen under different concentrations was elucidated, and their effects on the volume compression modulus and Poisson ratio were discussed.

Dielectric behaviour of magnetic hybrid materials

Abstract The objectives of this work include the analysis of electrical and magnetic properties of magneto-elastic hybrid materials with the intention of developing new techniques for sensor and actuator applications. This includes the investigation of dielectric properties at both low and high frequencies. The behaviour of capacitors whose dielectrics comprise magnetic hybrid materials is well known. Such interfacial magnetocapacitance can be varied according to magnetic content, magnetic flux density and the relative permittivity of the polymer matrix together with other dielectric content. The basic function of trapping electrical charges in polymers (electrets) is also established technology. However, the combination of magnetoactive polymers and electrets has led to the first electromagnetic device capable of adhering to almost any material, whether magnetically susceptible or not. During the course of this research, in addition to dielectrics, electrically conductive polymers based on (PDMS) matrices were developed in order to vary the electrical properties of the material in a targeted manner. In order to ensure repeatable results, this demanded new fabrication techniques hitherto unavailable. The 3D printing of silicones is far from being a mature technology and much pioneering work was necessary before extending the usual 3 d.o.f. to include orientation about and diffusion of particles in these three axes, thus leading to the concept of 6D printing. In 6D printing, the application of a magnetic field can be used during the curing process to control the particulate distribution and thus the spatial filler particle density as desired. Most of the devices (sensors and actuators) produced by such methods contain levels of carbonyl iron powder (CIP) embedded magnetic filler of up to 70 wt%. Contrary to this, a hitherto neglected research area, namely magnetoactive polymers (MAPs) having significantly lower magnetic particle concentrations (1 to 3 wt% CIP) were also investigated. With filler concentrations lower than 3 wt%, structures are formed which are completely absent at higher filler levels. CIP concentrations in the range of 1wt% demonstrate the formation of toroidal structures. Further development of coherent rings with a compact order results as filler concentrations increase towards 2 wt%. Above 3 wt% the structure eventually disintegrates to the usual random order found in traditional MAP with higher CIP content. Structured samples containing 1%–3 wt% CIP were investigated with the aid of X-ray tomography where solitary ring structures can be observed and eventually the formation of capillary doubles. Over wavelengths ranging from 1 to 25 µm, spectroscopic analysis of thin film MAP samples containing 2 wt% CIP revealed measurable magnetic-field-dependent changes in IR absorption at a wavenumber 2350 (λ = 4.255 µm). This was found to be due to the diamagnetic susceptibility of atmospheric carbon dioxide (CO2). Consequently, the first potential application for sparse matrix MAPs was found.

A new 3D model for magnetic particle imaging using realistic magnetic field topologies for algebraic reconstruction

We derive a new 3D model for magnetic particle imaging (MPI) that is able to incorporate realistic magnetic fields in the reconstruction process. In real MPI scanners, the generated magnetic fields have distortions that lead to deformed magnetic low-field volumes with the shapes of ellipsoids or bananas instead of ideal field-free points (FFP) or lines (FFL), respectively. Most of the common model-based reconstruction schemes in MPI use however the idealized assumption of an ideal FFP or FFL topology and, thus, generate artifacts in the reconstruction. Our model-based approach is able to deal with these distortions and can generally be applied to dynamic magnetic fields that are approximately parallel to their velocity field. We show how this new 3D model can be discretized and inverted algebraically in order to recover the magnetic particle concentration. To model and describe the magnetic fields, we use decompositions of the fields in spherical harmonics. We complement the description of the new model with several simulations and experiments, exploring the effects of magnetic fields distortion and reconstruction parameters on the reconstruction.

Formation and migration of magnetic particles associated with iron oxide transformation at a hillslope scale

Iron oxides are widespread on the surface of the Earth as a weathering product of iron-bearing primary minerals, which often accompany the enrichment of magnetic particles under aerobic conditions. The magnetic properties determined by the content and ratio of magnetic particles have been widely employed in paleoclimate reconstructions and erosion simulations. However, water redistribution at a slope scale could cause a phase transformation of iron oxides and a corresponding change in magnetic properties. In this study, we investigated a catena with a distinct soil colour change from red to yellow, which commonly occurs in tropical and subtropical hilly and mountainous regions. From upslope to downslope, the free iron oxide content decreases while the amorphous iron oxide content increases. The hematite diminishes significantly while the goethite shows little variation. The ferrimagnetic particles decrease in phase with hematite except for the finest superparamagnetic particles. However, the concentration of finer ferrimagnetic particles relative to coarser particles and the concentration of ferrimagnetic particles relative to antiferromagnetic particles both increase downslope. This increase validates the formation path of ferrimagnetic particles as an intermediate product of hematite but reveals more significant particle growth and transformation into hematite with decreasing water activity in granitic soils with low iron content. In addition, these processes could be enhanced by the preferential migration of the finest ferrimagnetic particles or their transformation from amorphous iron oxides enriched downslope. The slope-scale redistribution of iron oxides and related magnetic particles increases their uncertainty in paleoclimate reconstruction and erosion simulation but brings promising prospects to trace geomorphic evolution and hydrologic change over the long term.

Theoretically optimized hybrid magnetic nanoparticle concentrations for functional gradient nanocomposites

Magnetically actuated functional gradient nanocomposites have widely been used for ultra-durable biomimetic interfaces and surfaces. However, the mechanical and thermal mismatches in integrated systems containing dissimilar materials or structures usually cause failures. By modulating the concentration of magnetic particles, a suitable mechanical gradient morphology can be generated to match different integrated systems. In this work, a new model is developed to describe magnetic particle motion under the magnetic field. Hybrid nano-reinforcements with two different magnetic particle sizes and concentrations were employed to optimize the magnetic particle concentration gradient. It was observed that the diversification of concentration distribution can be achieved by tuning the sizes and concentrations of nanoparticles. The present study, therefore, contributes toward the understanding of the transport mechanism of magnetic-field-actuated functional gradient nanocomposites and provides guidance for experiments to design ultra-durable biomimetic interfaces and surfaces.

Fabrication of Magnetic Polymer Nanocomposites Using Inkjet 3D Print Technology

Tailored magnetic nanocomposites have applications ranging from communications technologies to medical devices. Using a novel 3D fabrication technique that combines thermal inkjet and powder bed fusion print technologies, magnetic composites were fabricated by jetting magnetic nanoparticle containing ink into a polymer powder bed and then heat fusing the ink/polymer matrix. The goals were to demonstrate the feasibility of nanocomposite fabrication with controllable magnetic properties by varying the volume fraction of magnetic ink jetted into the polymer as well as to experimentally validate the effective medium theory based model developed to predict the permeability of the composites as a function of its magnetic particle concentration. As expected, magnetic susceptibility and saturation magnetization were seen to increase with the volume fraction of magnetic particles in the composites.

Investigation on the Formation Mechanism of Crack Indications and the Influences of Related Parameters in Magnetic Particle Inspection

The recent rapid development of industrial cameras and machine learning has brought new vitality to the very traditional flaw detection method, namely, magnetic particle inspection (MPI). To fully develop automatic fluorescent MPI technology, two main issues need to be solved urgently—the lack of theoretical analysis on the formation of the crack indications, and quantitative characterization methods to determine the crack indications. Here, we carry out a theoretical analysis and an experimental approach to address these issues. Theoretical models of the acting force of the leakage magnetic field were established. Subsequently, the impacts of different magnetic field strengths (1000–9000 A/m) and magnetic particle concentrations (0.5–30 mL/L) on the adsorption critical distance were analyzed. The models were solved by numerical calculations in MATLAB. In addition, a single variable control experiment was conducted to study the effects of crack images. In order to determine the quality of the crack image, three characteristic parameters were investigated, such as indication gray scale, background gray scale, and contrast ratio, were provided. The theoretical magnetic particle concentration range provided a guidance value for automated fluorescent MPI. Experimental results revealed that the optimal magnetic particle concentration was 3–4 mL/L, and, under this condition, the contrast between the crack indications and the background of crack images was obvious.