NdFeB Research Articles

Influence of the NiFe/Cu/NiFe Structure Dimensions and Position in External Magnetic Field on Resistance Changes under the Magnetoresistance Effect.

The subject of this work is NiFe/Cu/NiFe thin-film structures made by magnetron sputtering and showing the phenomenon of magnetoresistance. Three series of samples differing in spatial dimensions and thickness of the Cu spacer were produced. During the sputtering process, an external magnetic field of approx. 10 mT was applied to the substrate. Measurements of the resistance of the structures were carried out in the field of neodymium magnets in three different positions of the sample in relation to the direction of the field. The measurements allowed us to indicate in which position the structures of different series achieved the greatest changes in resistance. For each of the three series of layer systems, the nature of changes in the determined coefficient of giant magnetoresistance ΔR/R remained similar, while for the series with the smallest copper thickness (2.5 nm), the coefficient reached the highest value of about 2.7‱. In addition, impedance measurements were made for the structures of each series in the frequency range from 100 Hz to 100 kHz. For series with a thinner copper layer, a decrease in impedance values was observed in the 10-100 kHz range.

정수기 빌트인용 SPM type BLDC 모터 토크제어를 위한 모터설계 및 약계자 제어기 설계에 관한 연구

The system for water purifiers requires a motor with a constant speed, high torque, low noise, and low power. AC motors have low starting torque, and DC motors have difficulty in replacing brushes, generate noise, and are difficult to maintain. This study uses a high-density energy magnet called a neodymium magnet to design and control an SPM brushless DC (BLDC) motor to control high torque. This paper proposes the control and design of BLDC motors using the weak field method.

EFFECT OF MAGNETIC FIELD AND ENVIRONMENTAL PH ON THE ADSORPTION EFFICIENCY OF CELLS OF THE GENUS LACTOBACILLUS

Subject. Adsorption of probiotic cultures Lactobacillus acidophilus, namely strains 27 and Narine, and Lactobacillus plantarum, on high-dispersed silica. Purpose. The purpose of this study was to investigate the influence of a magnetic field with intensities of 0.03 and 0.09 T and the pH of the medium on the efficiency of cell adsorption of Lactobacillus probiotic strains. Method. Microbiological and biotechnological methods were applied in this research. Hydrogels based on high-dispersed silica "Enterosgel" and "Toxin.NET" were used as adsorbents. Neodymium magnets with intensities of 0.03 T and 0.09 T were employed to create the magnetic field. The efficiency of adsorption was evaluated by the cell survival of probiotic cultures after adsorption on hydrogel preparations under the influence of the magnetic field and in the case of pH adjustment by adding acid or alkali. The functional properties of the obtained composite preparations were assessed by the time of clot formation after milk fermentation and its acidity. Results. The research results demonstrated that immobilized cells of Lactobacillus acidophilus on the hydrogel of methylsilicic acid had enhanced protection not only against harsh conditions of the gastrointestinal tract (low pH and bile influence) but also against magnetic fields with intensities of 0.03 T and 0.09 T, which had an overall negative impact on native (non-immobilized) cells. The functional activity of cells immobilized in this way on the hydrogel based on high-dispersed silica "Enterosgel," evaluated by acidity and clot formation time, was only slightly reduced: up to 4,3-11,3%. This confirms the assumption that the assessment of cell survival by the Koch's cup method does not fully correspond to the real state of the cells. It was also determined that conducting adsorption in the pH range below 4 is impractical, and the optimal conditions for L. plantarum adsorption were in the pH range of 6 to 7. Scope of results. The research findings can be utilized for the development of complex probiotic preparations based on high-dispersed silica, which may be appropriate for preserving the functionality of probiotic cells used for starter cultures or in the production of dietary supplements containing beneficial microorganisms.

Immobilized acetylcholinesterase in magnetic nanoparticles for in-line inhibition studies using a capillary electrophoresis system

Enzyme assays can be performed with the capillary electrophoresis technique (CE) in many approaches, such as the immobilized enzyme micro-reactor. Acetylcholinesterase is a promising enzyme to be used when pursuing such a method, as it has already been explored in the proposal of similar methods of miniaturizing enzyme assays. The present work proposes a novel enzyme micro-reactor, based on the anchorage of the enzyme on magnetic nanoparticles of MnFe2O4, with chitosan and glutaraldehyde as the cross-linker in the capillary by means of an arrange of neodymium magnets. The calculated Km of the enzyme evaluated by this method was 1.12 mmol L−1, comparable to other studies in the literature that utilizes immobilized enzymes. Also, IC50 for neostigmine was assessed in 3 different micro-reactors, with an average of 29.42 ± 3.88 μmol L−1. In terms of the micro-reactor stability, it was possible to perform at least 25 experiments with assembled micro-reactor. The method was applied to hydroalcoholic extracts of 7 plant species. Plinia cauliflora had the best result, with 42.31 ± 6.81% of enzyme inhibition in a concentration of 100 mg L−1.

Development of a novel microdevice for sorptive extraction under a green analytical chemistry approach: Application for bioanalytical determination of Ibuprofen

This study proposes a novel device called micro polymeric magnetized bar adsorptive extraction (µ-PMBAE), as an extraction and enrichment technique for trace analysis in aqueous samples. These micro-bar absorbent devices were prepared using easily accessible and low-cost materials, incorporating different sorbent materials into a polymer and introducing a small piece of neodymium magnet. Several stability tests were applied to determine their robustness, stability, and weight variation; finally, ibuprofen concentration in urine samples was determined, demonstrating the applicability of extraction devices under a green analytical chemistry approach. The µ-PMBAE showed remarkable advantages since different sorbents can be added to the hot melt glue. This tunes the interaction with the analytes to become more specific in the extraction. Likewise, the magnetic ability makes it possible to carry out extraction without using an extra stir bar, matching its performance with the traditional commercially based on polydimethylsiloxane phase. The proposed analytical method demonstrated excellent performance concerning high recovery percentages, adequate coefficients of variation, and low detection limits.

Development of a novel microdevice for sorptive extraction under a green analytical chemistry approach: Application for bioanalytical determination of Ibuprofen

This study proposes a novel device called micro polymeric magnetized bar adsorptive extraction (µ-PMBAE), as an extraction and enrichment technique for trace analysis in aqueous samples. These micro-bar absorbent devices were prepared using easily accessible and low-cost materials, incorporating different sorbent materials into a polymer and introducing a small piece of neodymium magnet. Several stability tests were applied to determine their robustness, stability, and weight variation; finally, ibuprofen concentration in urine samples was determined, demonstrating the applicability of extraction devices under a green analytical chemistry approach. The µ-PMBAE showed remarkable advantages since different sorbents can be added to the hot melt glue. This tunes the interaction with the analytes to become more specific in the extraction. Likewise, the magnetic ability makes it possible to carry out extraction without using an extra stir bar, matching its performance with the traditional commercially based on polydimethylsiloxane phase. The proposed analytical method demonstrated excellent performance concerning high recovery percentages, adequate coefficients of variation, and low detection limits.

Increase in demand for critical materials under IEA Net-Zero emission by 2050 scenario

Increasing the deployment of low-carbon technologies on a global scale is critical for mitigating climate change and achieving net-zero emissions (NZE) by 2050. Implementing such technologies requires a rapidly increasing supply of both critical and non-critical materials. We developed a scenario-based dynamic material stock flow model to calculate the critical material requirements of major low-carbon technologies under the newly released International Energy Agency (IEA) NZE by 2050 scenario. Our results show that most of the metal demand related to photovoltaics would reach its peak around 2035 and then gradually decline, whereas the demand for rare earth elements (REEs) continue to surge. Over the past decade, wind turbines have mainly been responsible for the consumption of neodymium iron boron (NdFeB) magnets containing REEs; however, this will soon be superseded by electric motors (EMs) primarily used in for electric vehicles (EVs). In the short term, increased recycling will have a relatively low impact on the demand for primary resources. With current recycling rates, the secondary supply of REEs will contribute <1% to the demand in 2050, however, aggressive recycling strategies could increase the contribution to 35%. Furthermore, we contend that alternative technologies based on non-critical materials could address the mismatch between supply and demand to resolve the issues presented by material scarcity.

Energy harvesting using linear type magnetostrictive transducer for real-time application

Economic and social development of nations across the globe is demanding enormous need for energy and power resources. Energy production using safe and renewable sources can aid in mitigating the release of greenhouse gases and avoiding the devastating climate changes. In the present case, a linear type magnetostrictive transducer device is designed by employing Terfenol-D magnetostrictive rods for renewable energy harvesting application. A linear device was designed with two Terfenol-D rods, three permanent magnets (neodymium magnets), springs, and primary and secondary coils. Terfenol-D rod crystallizes in cubic Laves phase and exhibits the saturation magnetostriction value of 1242 × 10−6 at the field of 2.5 kOe. An equivalent circuit is constructed for the induced magnetic flux in the designed transducer device. Frequency and wave form dependent output voltage is examined in the designed energy harvesting device. A square wave at the applied frequency of 2200 Hz (100 mA current) produces a maximum output voltage of 4.91 V. Sine and triangle waves produce 3.38 and 2.82 V, respectively, at 1700 and 1600 Hz. The induced voltage is sufficient to ignite the light emitting diode. A linear type magnetostrictive transducer can be employed as a potential renewable energy source for real-time application with moderate output voltage.

Analysis of PEC technique and external magnetic fields for detection of corrosion under insulation: 3D finite element model

Metal piping in industrial plants is subject to corrosion under insulation, which reduces the wall thickness and limits service life and operating conditions. The Pulsed Eddy Current (PEC) technique can be effective in the inspection of isolated metallic materials. However, changes in magnetic permeability make its use difficult in ferromagnetic steels. In this work, we used Neodymium magnets to magnetize the material during tests with a probe. We developed a 3D finite element model to reproduce the magnetic field of the PEC probe and identify defects under insulation. Theoretical results satisfactorily matched the experimental results.

Determination of hexanal and heptanal in saliva samples by an adapted magnetic headspace adsorptive microextraction for diagnosis of lung cancer

In this work, an analytical method for the determination of two endogenous aldehydes (hexanal and heptanal) as lung cancer biomarkers in saliva samples is presented for the first time. The method is based on a modification of magnetic headspace adsorptive microextraction (M–HS–AME) followed by gas chromatography coupled to mass spectrometry (GC-MS). For this purpose, an external magnetic field generated by a neodymium magnet is used to hold the magnetic sorbent (i.e., CoFe2O4 magnetic nanoparticles embedded into a reversed-phase polymer) in the headspace of a microtube to extract the volatilized aldehydes. Subsequently, the analytes are desorbed in the appropriate solvent and the extract is injected into the GC-MS system for separation and determination. Under the optimized conditions, the method was validated and showed good analytical features in terms of linearity (at least up to 50 ng mL−1), limits of detection (0.22 and 0.26 ng mL−1 for hexanal and heptanal, respectively), and repeatability (RSD ≤12%). This new approach was successfully applied to saliva samples from healthy volunteers and those with lung cancer, obtaining notably differences between both groups. These results reveal the prospect of the method as potential diagnostic tool for lung cancer by saliva analysis. This work contributes to the Analytical Chemistry field presenting a double novelty: on the one hand, the use of M–HS–AME in bioanalysis is unprecedentedly proposed, thus expanding the analytical potential of this technique, and, on the other hand, the determination of hexanal and heptanal is carried out in saliva samples for the first time.

Magnetic control of self-assembly and disassembly in organic materials

Because organic molecules and materials are generally insensitive or weakly sensitive to magnetic fields, a certain means to enhance their magnetic responsiveness needs to be exploited. Here we show a strategy to amplify the magnetic responsiveness of self-assembled peptide nanostructures by synergistically combining the concepts of perfect α-helix and rod-coil supramolecular building blocks. Firstly, we develop a monomeric, nonpolar, and perfect α-helix (MNP-helix). Then, we employ the MNP-helix as the rod block of rod-coil amphiphiles (rod-coils) because rod-coils are well-suited for fabricating responsive assemblies. We show that the self-assembly processes of the designed rod-coils and disassembly of rod-coil/DNA complexes can be controlled in a magnetically responsive manner using the relatively weak magnetic field provided by the ordinary neodymium magnet [0.07 ~ 0.25 Tesla (T)]. These results demonstrate that magnetically responsive organic assemblies usable under practical conditions can be realized by using rod-coil supramolecular building blocks containing constructively organized diamagnetic moieties.

Gold conjugated-magnetite nanoparticles for magnetic concentration towards reproducibility and repeatability of SERS measurements

Variables such as uncontrolled colloid aggregation, and even the natural motion of particles named Brownian motion, lead to small variations in the molecular position and arrangement between molecule and nanoparticles, thus influencing SERS magnitude. To address this issue, we synthesized gold conjugated-magnetic nanoparticles (AuMNP) as a SERS platform for dopamine (DA) detection. Unlike conventional colloids such as silver and gold, which are unable to provide SERS for DA, the AuMNP not only yielded SERS signal but also improved repeatability and reproducibility. Under a magnetic concentration using a neodymium magnet, the standard deviation of ten measurements was found to be 19.4 versus 800 (arb.un.) for the magnetically concentrated and dispersion measurements, respectively. The hot spots formation in the AuMNP and the possible DA − AuMNP interactions are in the origin of the obtained SERS signal. Additionally, the DA SERS signal varied with concentration according to the Freundlich isotherm model, indicating multilayer adsorption. The limit of detection was in order of 10–6 mol/L without further optimizations.

Supermagnet Braking System

In this project Super magnet brake is the innovative concept based on the magnetic attraction of the conducting metals. A super magnet brake, like a conventional friction brake, is responsible for slowing an object, such as a train or a roller coaster. Unlike friction brakes, which apply pressure on two separate objects, eddy current brakes slow an object by creating eddy currents through electromagnetic induction which create resistance, and in turn either heat or electricity.

Investigating Metal–Tributyl Phosphate Complexes during Supercritical Fluid Extraction of the NdFeB Magnet Using Density Functional Theory and X-ray Absorption Spectroscopy

Supercritical fluid extraction (SCFE) is gaining significant interest as a green technology for the recycling of end-of-life waste electrical and electronic equipment (WEEE). Neodymium iron boron (NdFeB) magnets, which contain large quantities of critical rare-earth elements such as neodymium, praseodymium, and dysprosium, are widely used in wind turbines and electric/hybrid vehicles. Hence, they are considered a promising secondary resource for these elements when they reach their end-of-life. Previously, the SCFE process was developed for recycling WEEE, including NdFeB; however, the process mechanism remains unexplored. Here, density functional theory, followed by extended X-ray absorption fine structure and X-ray absorption near-edge structure analyses, are utilized to determine the structural coordination and interatomic interactions of complexes formed during the SCFE of the NdFeB magnet. The results indicate that Fe(II), Fe(III), and Nd(III) form Fe(NO3)2(TBP)2, Fe(NO3)3(TBP)2, and Nd(NO3)3(TBP)3 complexes, respectively. This theory-guided investigation elucidates the complexation chemistry and mechanism during the SCFE process by rigorously determining the structural models.

A study on demagnetization heat treatment of waste neodymium iron boron (NdFeB) magnets by using computer simulation

In this study, demagnetization heat treatment at 100 ∼400 °C is studied by using computer simulation to secure the optimal demagnetization heat treatment conditions for waste neodymium iron boron (NdFeB) permanent magnets. From the computer simulation, the temperature of the magnet during heat treatment is higher than the set temperature by up to 6 °C. Delay time occurs when the furnace internal temperature and magnet temperature reached the set temperature. A delay time of 15 minutes in an air atmosphere and 10 minutes in a nitrogen atmosphere occurs. The Nd magnet was completely demagnetized at 300 °C as the magnetic flux decreased when the heat treatment temperature increased up to 250 °C. The fully demagnetized magnet could be magnetized to the level of a new magnet. It was confirmed that NdFeB magnets heat treated up to 350 °C in a nitrogen atmosphere can be reusable due to stable demagnetization being possible without surface change.

Permanent neodymium magnets in the Russian wind power industry

This article is devoted to the problems of wind energy in Russia. One of the key issues in the development of wind energy in our country is the uninterrupted supply of permanent neodymium magnets and raw materials for their manufacture to wind generator manufacturers. After the collapse of the Soviet Union, several enterprises with the necessary competencies and technological equipment to produce magnets based on rare earth metals (REMs) survived in the country. However, the problem is that Russia does not have a complete production chain to the level of oxides, as well as individual rare earth elements and alloys based on them. All permanent magnets based on rare earth metals are imported, and supply interruptions negatively affect the work of high-tech companies, as well as enterprises of the fuel and energy complex and the military–industrial complex. The article analyzes the need of the country's wind energy industry for permanent neodymium magnets, the full production cycle of which can become one of the incentives to restore the production chain of rare earth metals and products based on them.

Magnetic guidewire steering at ultrahigh magnetic fields.

With remote magnetic steering capabilities, magnetically actuated guidewires have proven their potential in minimally invasive medical procedures. Existing magnetic steering strategies, however, have been limited to low magnetic fields, which prevents the integration into medical systems operating at ultrahigh fields (UHF), such as magnetic resonance imaging (MRI) scanners. Here, we present magnetic guidewire design and steering strategies by elucidating the magnetic actuation principles of permanent magnets at UHF. By modeling the uniaxial magnetization behavior of permanent magnets, we outline the magnetic torque and force and demonstrate unique magnetic actuation opportunities at UHF, such as in situ remagnetization. Last, we illustrate the proposed steering principles using a magnetic guidewire composed of neodymium magnets and a fiber optic rod in a 7-Tesla preclinical MRI scanner. The developed UHF magnetic actuation framework would enable next-generation magnetic robots to operate inside MRI scanners.

Influence of magnetic field exposure on methane hydrate

Gas hydrate mitigation is considered a painstaking process in the oil and gas industry. Chemically, mono ethylene glycol (MEG) is used to control the gas hydrate formation. However, gas hydrate formation can also be affected by an external magnetic field under certain conditions such as subsea production equipment that can generate a magnetic field. This magnetic field could influence the physical behaviour of the gas hydrate conditions of the transported fluid within the subsea production pipelines. The objectives of this research were to assess the effects of exposing water and 20 wt % MEG solution to the magnetic field of 13,499 Gauss, neodymium magnet, on methane hydrate formation in correlation with field exposure time and memory effects. This study determined that, for the water solution, there was a proportional, incremental trend between the magnetic field exposure time and its memory effect for exposures of 172, 258 and 387 h. The dissociation temperatures of the magnetized solutions were raised and had different hydrate developments. However, no effects were found on the 20 wt % MEG solution. It has been inferred from this outcome that the addition of MEG impacted on the water molecules numbers within the hydration shell. The application of the potential magnetic effect as a control method can provide in-depth and better understanding of the hydrate behaviour and mechanism at subsea conditions.

Clinical effect of magnetic compression anastomosis on ureterostenosis after kidney transplantation.

Clinical effect of magnetic compression anastomosis on ureterostenosis after kidney transplantation.

Magnetic field hydrocooling system: Effect of field intensities on the cooling characteristics of three different leavy vegetables

The physiological changes occurring during postharvest of leafy vegetables affect quality. To address this, several cooling technologies that utilize physical fields like magnetic fields (MFs) have been proposed. The application of MFs in the cooling of leafy vegetables however remains a substantial controversy among the food engineers. Therefore, the effectiveness should be clarified by experiments. In the current study, the effect of MFs (at 534.1 mT, 458.0 mT, and 396.8 mT) on hydrocooling process of three different leafy vegetables including jute mallow, fluted pumpkin, and bitter leaf was investigated by using a specially designed hydrocooling system facilitated with magnetic field (also known as magnetic field hydrocooling; MFHC) generated from a Neodymium permanent magnet. The investigation included the comparison of the cooling curves, physiological loss in weight (PLW), microbial loads, and observation of microstructures. Based on the results of the experiment, it was observed that the weak magnetic fields provided significant improvement on the hydrocooling technique as well as the quality of hydrocooled vegetables. The MFHC assisted by Neodymium magnet (at 396.8 mT) provided higher cooling rate (at P ≤ 0.05) when compared with conventional room cooling, reduced microbial loads significantly from 8.40 × 105 to 5.86 × 105 CFU/ml, 7.03 × 105 to 5.89 × 105 CFU/ml and 6.00 × 105 to 4.0 × 105 CFU/ml (at P ≤ 0.05) for jute mallow, fluted pumpkin and bitter leaf respectively. In addition, hydrocooling-assisted by magnetic field (at 396.8 mT) is more effective in the preservation of the microstructures. The study indicates that the MFHC technology enhances cooling process and preserves the leafy vegetables, thus pose great potential in the food industry. Practical applicationsLeafy vegetables deteriorate faster after harvest; hence, there is a need to cool them in order to extend their shelf-life. MFHC technique has great potentials in preservation of leaves, with the advantage of minimum quality loss due to reduction in cooling time and microbial activities. Currently, innovative studies have been carried out on the use of MFHC technique to improve the cooling process and achieve better quality preservation. However, the findings presented in this work can provide detail insights on the quality of some leafy vegetables that were cooled by MFHC, and give some guidance for further developments of MFHC technology.