Ceramic Magnets Research Articles

Selective enhancement of 1H signal from water and oil in porous media at low field with Overhauser DNP.

In porous media MR studies, discriminating between oil and water presents a challenge because MR lifetimes are often similar and spectra overlap. Low saturations might suggest an experimental strategy of increasing the static field for increased sensitivity, but susceptibility effects are exacerbated at higher field. Overhauser dynamic nuclear polarization, effective at low static field, was employed with water and oil-soluble nitroxide to selectively enhance water and oil signals. We employ a home-built 2MHz ceramic magnet to achieve selective enhancement of water and oil, in bulk, and in a rock core. For imaging, we employ a 705kHz ceramic magnet with a 4 gauss/cm constant gradient configuration to image the hyperpolarized signal. A rock core flooding experiment was undertaken to highlight the advantages of Overhauser enhancement. A simple phase cycling technique may be employed to cancel the thermally polarized 1H signal to isolate the enhanced signal of interest.

A modular, low-field magnetic resonance design with pre-polarization for characterizing flows

We have recently demonstrated a magnetic resonance method using variable τ spin echoes to simultaneously determine both the average velocity and flow behavior index in a variety of pipe flows. In this work, we present a new, modular, low-field design built specifically for use with our methodology. The design is based on low-cost ceramic magnets. It consists of a sensor built using a pitched magnet arrangement in combination with several modular pre-polarizing units to facilitate a controlled pre-polarization length for measurements on flows that require a significant amount of time in a magnetic field to become polarized (e.g., aqueous solutions). Here, measurements made with this design are shown for a range of flow rates that span the laminar regime and into the turbulent regime.

SYNTHESIS STRUCTURAL AND MAGNETIC PROPERTIES OF TITANIUM DOPED MAGNESIUM ZINC FERRITE

Magnetic ceramics or ferrites are very well established group of magnetic materials which exhibits ferrimagnetism. It possess high electrical resistivity, low eddy current and dielectric loss which makes it superior than the other ordinary magnetic oxides that contain the ferric oxide (Fe₂O₃) as their basic magnetic compounds. The ceramic magnets are widely used in high frequency transformer application. [(Mg, Mn, F12o4)] spinels are used in square-loop application. Ceramic materials found application in nuclear physics. In nuclear reactors ceramics are used as core components. The studies include the preparation and analysis of Titanium doped Magnesium zinc ferrite. Here, Titanium doped magnesium zinc ferrite nanoparticles (NPS) were synthesized using solid state reaction method. Titanium doping can enhance the magnetic properties of magnesium zinc ferrite in several ways these can contribute to improved magnetic properties , such as increased magnetic moment, saturation magnetization, and magnetic ordering , making titanium – doped magnesium zinc ferrite a promising material for various applications including magnetic storage, sensors, and spintronics. According to the stoichiometric equation [Mg0.9Zn 0.1TixFe2-xO4] at different values of x, (x=0.1, 0.3) are synthesised. Calcination and sintering of the samples is made by high temperature PID controlled muffle furnace which can go up to 1000°C. The structural and magnetic properties are examined using XRD, FTIR and Curie temperature analysis. From the XRD analysis it revels the phase structure and lattice parameters of the samples. XRD analysis gives maximum intensity of (h k l) values as (3 1 1) in both cases. It also reveals that no secondary phases are produced during growth. That means the specimens FCC stacking. FTIR analysis of the samples done using Fourier transformer infrared spectroscopy. From this analysis it revels the detailed atomic structure and bonding of the samples. The bands obtained reveal spinal ferrite structure. Curie temperature of the specimens is determined by Curie temperature apparatus for the study of magnetic properties of the specimens.

Optimized distribution of black cylinder ceramic magnet with dual effects of magnetic field and thermal energy storage to enhance the productivity of conical solar distillers

Optimized distribution of black cylinder ceramic magnet with dual effects of magnetic field and thermal energy storage to enhance the productivity of conical solar distillers

Static Magnetic Properties and Morphological Behaviour of Mn and Zn Substituted Ca-hexaferrite by Ceramic Technic

Synthesis of M-type hexagonal ferrite compounds, Ca(CoTi)0.5(MnZn)x/2Fe11-xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) prepared by ceramic technic. Mn and Zn ions substituted to find the magnetic characterizationat magnetic field of 10 kOe. XRD and SEM study have been done for getting the hexagonal structure of these samples. Due to the substitution of Mn and Zn ions saturation magnetization increases and magnetocrystalline anisotropy decreases. Due to the sub-latice site distribution the variations in magnetic parameters have been observed. Because of Mn and Zn ions substitution Curie temperature decreases by weakening of superexchange interaction. These materials can be used for various applications such aspermanent magnetic material, magnetic recording media, ferrofluids, sensors, microwave absorbing materials, ceramic magnets in loud speakers and rotors in small DC motors by studying various magnetic parameters from VSM characterization.

PENGARUH VARIABEL CELAH UDARA TERHADAP FLUKS MAGNET PADA GENERATOR PERMANEN MAGNETIK AXIAL FLUKS

Generators that use permanent magnets do not require initial excitation to produce voltage. where the generator design is an axial flux type using a ceramic type permanent magnet (NdFeB), and uses two flanking stator rotors. For electricity use, the AC voltage is changed to DC voltage using a rectifier for charging the accumulator. The air gap in an axialflux generator is the distance between the rotor and stator. The air gap is also a place for the magnetic field to move through the coils in the stator which ultimately produces a magnetic flux value which will influence the amount of induced voltage produced. The faster the rotation produced, the greater the voltage produced, but the frequency value will also increase, so that this generator is only limited to 400 rpm rotation, at a frequency value of 50 Hz, producing an effective voltage of ± 22 V with an air gap distance ( δ) is 2 mm, the frequency measurement has an error of 10-20 Hz and an error percentage of 5-10%, with the results of the induced current measurement having the same voltage

Cold sintering process for densification of Fe3O4 ceramic magnets with improved properties

Iron oxide-based ferrite ceramics, widely applied in high-frequency applications, are conventionally produced through high-temperature sintering processes, often resulting in grain growth and phase transformation. In this study, we used a cold sintering process (CSP) with oxalic acid (OA) as a solvent to consolidate iron oxide (Fe3O4) ceramics at a low temperature of 160 °C. The OA-assisted CSP technique has demonstrated a remarkable capacity to facilitate the dissolution and redeposition of iron oxide ions, leading to the interconnection of Fe3O4 particles, forming densely packed ceramics even at low-temperature sintering. Importantly, CSP maintained particle sizes and hindered phase transitions of Fe3O4. The OA concentrations in CSP had a minimal impact on crystal structure and magnetic properties, but it significantly enhanced microstructural features, density, hardness, and electrical resistance. Compared to reference samples prepared without an aqueous solution or with water alone, the CSP-prepared Fe3O4 ceramics with OA exhibited substantially improved density (a relative density of ∼80 %), mechanical properties (Vickers hardness of 3.5–4.0 GPa), magnetic properties (saturation magnetization >70 emu/g), and electrical resistance (electrical conductivity ∼10−3 S/cm at 102–106 Hz). These findings demonstrate a novel approach to fabricating Fe3O4 ceramics at significantly lower temperatures while still achieving properties comparable to those sintered at high temperatures.

A low-field ceramic magnet design for magnetic resonance

We describe the design of a low-field portable magnet, based on two ceramic magnets, separated by a distance, with their magnetic poles aligned to create a large homogeneous region with a field strength of 425 gauss. Ceramic magnets are an uncommon choice compared to Neodymium Iron Boron magnets for low-field magnetic resonance but are preferable for our purposes to create a homogeneous region at lower field strength. The low cost of large ceramic magnets results in an inexpensive design with a large measurement volume. The magnets rest in a 3D-printed structure, which allows for the magnets to be moved by hand so the experimentalist has control over the field topology. To test the utility of the design, we explored an Overhauser dynamic nuclear polarization experiment with an aqueous solution of 4-Hydroxy-TEMPO. We also explored a simple flow measurement employing the ceramic magnets at a 6-degree pitch, creating a 14.6 gauss/cm constant gradient.

Sintering in seconds, elucidated by millisecond in situ diffraction

Materials, when sintered at high temperatures, undergo structural changes on multiple, hierarchical length scales but getting realtime information on these changes is difficult. To address this challenge, we developed a custom-built sample environment that allows us to investigate the structural evolution of materials during sintering using high-energy two-dimensional synchrotron X-ray diffraction (2D-XRD). Changes in the structure of SrFe12O19 ceramic magnet at multiple length scales were tracked in situ and modelled with millisecond time-resolution. In addition, we also demonstrated the ability to perform quantitative texture analysis from individual 2D-XRD images with a time resolution of 4 ms each. Owing to the high brightness X-ray source and advanced X-ray detectors, the evolution of crystallographic texture could be followed during sintering. This in situ approach can aid understanding of the synthesis–structure–property relationships in sintered materials, enabling the development of improved functional materials.

Remanence Increase in SrFe12O19/Fe Exchange-Decoupled Hard-Soft Composite Magnets Owing to Dipolar Interactions.

In the search for improved permanent magnets, fueled by the geostrategic and environmental issues associated with rare-earth-based magnets, magnetically hard (high anisotropy)-soft (high magnetization) composite magnets hold promise as alternative magnets that could replace modern permanent magnets, such as rare-earth-based and ceramic magnets, in certain applications. However, so far, the magnetic properties reported for hard-soft composites have been underwhelming. Here, an attempt to further understand the correlation between magnetic and microstructural properties in strontium ferrite-based composites, hard SrFe12O19 (SFO) ceramics with different contents of Fe particles as soft phase, both in powder and in dense injection molded magnets, is presented. In addition, the influence of soft phase particle dimension, in the nano- and micron-sized regimes, on these properties is studied. While Fe and SFO are not exchange-coupled in our magnets, a remanence that is higher than expected is measured. In fact, in composite injection molded anisotropic (magnetically oriented) magnets, remanence is improved by 2.4% with respect to a pure ferrite identical magnet. The analysis of the experimental results in combination with micromagnetic simulations allows us to establish that the type of interaction between hard and soft phases is of a dipolar nature, and is responsible for the alignment of a fraction of the soft spins with the magnetization of the hard. The mechanism unraveled in this work has implications for the development of novel hard-soft permanent magnets.

High-Performance Hexaferrite Ceramic Magnets Made from Nanoplatelets of Ferrihydrite by High-Temperature Calcination for Permanent Magnet Applications

Highly aligned ceramic hexaferrite magnets with high-energy products (BH)max and a density exceeding 90% of theoretical density have been fabricated. The precursors were an antiferromagnetic powder, a six-line ferrihydrite mixed with SrCO3, and a grain growth inhibitor SiO2. Conventional cold compaction of the precursor powders was employed prior to calcination at temperatures of 1050, 1150, and 1250 °C. The influence of calcination temperature and magnetic properties has been systematically studied in the produced ceramic magnets. Conventional cold compaction is a favorable route for industrial production when compared with other compaction techniques like spark plasma sintering, hot compaction, or electroforging. A high (BH)max of 25.2 kJ/m3 was obtained for the best magnet along with an appreciable coercivity, Hc, of 187 kA m–1, a high squareness ratio, Mr/Ms, of 0.84, and a saturation magnetization, Ms, of 73 A m2/kg. Texture and crystallite size analysis were extracted from 2D synchrotron transmission powder diffraction measurements. We have demonstrated that high-performance bulk magnets for permanent magnet applications can be produced from nonmagnetic interacting crystallites mixed with a grain growth inhibitor without applying a magnetic field for alignment.

Permanent Magnet Selections for AFPM Disc Generators

In this article, the field (FEM) and analytical analyses were used for the optimal selection of magnets material for the Axial Flux Permanent Magnet Generator (AFPMG), without building the prototype before. The tested generator is an axial flux machine which consists of a single stator and two rotor discs with Permanent Magnets (PM). Three-dimensional (3D) ANSYS Maxwell package was used for magnetostatic and transient field (FEM) simulations. Two types of PM were selected for the analysis: Ceramic (also known as “Ferrite”) magnets made from Strontium Ferrite powder and Neodymium Iron Boron magnets (NdFeB). The authors compared obtained electromotive forces (EMF) and generator powers for selected magnets materials, performed FFT analyses of voltages and currents and indicated the optimal solutions. In addition to the operational properties of the AFPMG, the magnet and manufacturing costs were compared.

A case study on thermal performance analysis of a solar still basin employing ceramic magnets

The energy and exergy analysis of a single slope solar stills using ceramic type rectangular and circular magnets in the basin was carried out in this study and compared to conventional solar still. The results showed that the rectangular magnet solar still (RMSS) had higher hourly productivity of about 5.8% and 13.7% than circular magnet solar still (CMSS) and conventional solar still (CSS), respectively. For 12 h of reading, the cumulative productivity in RMSS, CMSS, and CSS was observed at 3.15 kg/m2, 2.82 kg/m2, and 2.15 kg/m2, respectively. Compared to CMSS and CSS, the RMSS has enhanced its energy efficiency by 4.9% and 6.9%, respectively. The observed exergy efficiency in RMSS has increased to 3.4% and 17.2%, respectively, than CMSS and CSS. Due to sensible heat absorbed by magnets, the amount of exergy lost in the RMSS and CMSS basin is much less than in CSS. In economic analysis, the estimated produced water cost (PWC) of RMSS is 4.5% and 22.2% lower than the PWC estimated in CMSS and CSS, respectively. Overall, the results showed that the magnetization of saline water made the solar still work much better.

Effect of organic solvent on the cold sintering processing of SrFe12O19 platelet-based permanent magnets

In this work we have investigated the effect of the solvent during the processing of SrFe12O19 platelet-based permanent magnets by cold sintering process (CSP) plus a post-thermal treatment. Several organic solvents: glacial acetic acid, oleic acid and oleylamine have been analyzed, optimizing the CSP temperatures at 190−270 °C, under pressures of 375−670 MPa and 6−50 wt% of solvent. Modifications in the morphological and structural properties are identified depending on the solvent, which impacts on the magnetic response. Independently of the solvent, the mechanical integrity of ferrite magnets obtained by CSP is improved by a post-annealing at 1100 °C for 2 h, resulting in relative densities around 92 % with an average grain size of 1 μm and a fraction of SrFe12O19 phase >91 %. HC ≥ 2.1 kOe and MS of 73 emu/g are obtained in the final sintered ceramic magnets, exhibiting the highest HC value of 2.8 kOe for the magnet sintered using glacial acetic acid.

Hexaferrite-based permanent magnets with upper magnetic properties by cold sintering process via a non-aqueous solvent

The incessant technological pursuit towards a more sustainable and green future depends strongly on permanent magnets. At present, their use is widespread, making it imperative to develop new processing methods that generate highly competitive magnetic properties reducing the fabrication temperatures and costs. Herein, a novel strategy for developing dense sintered magnets based on Sr-hexaferrites with upper functional characteristics is presented. An innovative cold sintering approach using glacial acetic acid as novelty, followed by a post-annealing at 1100 °C, achieves a densification of the ceramic magnets of 92% with respect to the theoretical density and allows controlling the particle growth. After the cold sintering process, a fraction of amorphous SrO is identified, in addition to a partial transformation to α-Fe2O3 as secondary crystalline phase. 46 wt% of SrFe12O19 remains, which is mostly recuperated after the post-thermal treatment. These findings do not significantly modify the final structure of ferrite magnets, neither at short- nor long-range order. The innovative process has a positive impact on the magnetic properties, yielding competitive ferrite magnets at lower sintering temperatures with an energy efficiency of at least 25%, which opens up a new horizon in the field of rare-earth free permanent magnets and new possibilities in other applications.

Greener processing of SrFe12O19 ceramic permanent magnets by two-step sintering

With an annual production amounting to 800 kilotons, ferrite magnets constitute the largest family of permanent magnets in volume, a demand that will only increase as a consequence of the rare-earth crisis. With the global goal of building a climate-resilient future, strategies towards a greener manufacturing of ferrite magnets are of great interest. A new ceramic processing route for obtaining dense Sr-ferrite sintered magnets is presented here. Instead of the usual sintering process employed nowadays in ferrite magnet manufacturing that demands long dwell times, a shorter two-step sintering is designed to densify the ferrite ceramics. As a result of these processes, dense SrFe12O19 ceramic magnets with properties comparable to state-of-the-art ferrite magnets are obtained. In particular, the SrFe12O19 magnet containing 0.2% PVA and 0.6% wt SiO2 reaches a coercivity of 164 kA/m along with a 93% relative density. A reduction of 31% in energy consumption is achieved in the thermal treatment with respect to conventional sintering, which could lead to energy savings for the industry of the order of 7.109 kWh per year.

Analisis Perencanaan Jarak Celah Udara Pada Generator Axial

The generator uses a permanent magnet so it does not require initial excitation to generate a voltage. The generator design is axial flux type, uses ceramic type permanent magnet (NdFeB), uses two flanking stator rotors. For electricity use, the AC voltage is changed to DC voltage using a rectifier for charging the accumulator. The air gap in the axial generator is the distance between the rotor and the stator. The air gap is also a place for the transfer of the magnetic field through the coil on the stator to produce a magnetic flux value that affects the induced voltage in the coil. The faster the rotation, the greater the voltage generated. This axial generator that has been designed can produce a frequency of ± 50 Hz, an effective voltage of ± 22 V when the air gap is 2 mm, the frequency measurement has an error of 10-20 Hz and an error percentage of 5-10%, with the results of measuring the induced current that has a large the same voltage.

Design features and elemental/metal analysis of the atomizers in pod-style electronic cigarettes.

BackgroundThe atomizers of electronic cigarettes (ECs) contain metals that transfer to the aerosol upon heating and may present health hazards. This study analyzed 4th-generation EC pod atomizer design features and characterized their elemental/metal composition.MethodsEleven EC pods from six brands/manufacturers were purchased at local shops and online. Pods were dissected and imaged using a Canon EOS Rebel SL2 camera. Elemental analysis and mapping of atomizer components was done using a scanning electron microscope coupled with an energy dispersive x-ray spectrometer.ResultsEC pods varied in size and design. The internal atomizer components were similar across brands except for variations occurring mainly in the wicks and filaments of some products. The filaments were either Elinvar (nickel, iron, and chromium) (36.4%), nichrome (36.4%), iron-chromium (18.2%), or nickel (9%). Thick wires present in 55% of the atomizers were mainly nickel and were joined to filaments by brazing. Wire-connector joints were Elinvar. Metal air tubes were made of Elinvar (50%), nickel, zinc, copper, and tin (37.5%), and nickel and copper (12.5%). Most of the wick components were silica, except for two pods (PHIX and Mico), which were mainly ceramic. Connectors contained gold-plated nickel, iron-chromium multiple alloys of nickel, zinc, gold, iron, and copper. Wick chambers were made of Elinvar. Outer casings were either nickel, copper-tin, or nickel-copper alloys. Magnets were nickel with minor iron, copper, and sulfur. Some frequently occurring elements were high in relative abundance in atomizer components.ConclusionsThe atomizers of pods are similar to previous generations, with the introduction of ceramic wicks and magnets in the newer generations. The elements in EC atomizers may transfer into aerosols and adversely affect health and accumulate in the environment.

Bonded ferrite-based exchange-coupled nanocomposite magnet produced by Warm compaction

Many modern technologies require permanent magnets with combinations of properties that cannot be met by conventional metallic or ceramic magnets. Ferrite/polymer composite magnets are a type of rare-earth free magnet with a wide range of magnetic and material property combinations. The uncertainty surrounding the supply and pricing of rare-earth elements, along with environmental issues of using these elements, have motivated many researchers to develop high-performance ferrite-based magnets via an exchange spring method. The present study explores magnetite coated M-type ferrite nanocomposites synthesised via a hydrothermal and coprecipitation method, and investigates the mechanical and magnetic properties of warm compressed high-performance exchange-coupled nanocomposites in an epoxy matrix. We show how the powder-to-resin ratio and preparation conditions lead to optimised mechanical properties, and enhancement in the maximum energy product of the composite magnet by up to 120% compared to a commercial SrM bonded plasto-ferrite magnet. These high performance composite magnets can lower the final cost of ferrite based bonded magnets without reducing the permanent magnetic properties or can be used in applications that a ferrite magnet has inadequate performances.

Investigating the co-substitution impact of yttrium–nickel cations on lattice, morphological and magnetic parameters of SrM based ceramics

This study details the impact of the co-substitution of Y3+-Ni3+ ions for the Fe3+ ions on the structural, morphological and, magnetic parameters of SrM based SrYxFe12-2xNixO19 (0.00 ≤ x ≥ 0.25) (SrYFeNiO) ceramic magnets synthesized by the ceramic route. Rietveld refinement of XRD confirmed the hexagonal (P63/mmc (194), z = 2) SrFe12O19 phase for all and an additional rhombohedral (R-3c (167), z = 6) hematite Fe2O3 phase for x = 0.2, x = 0.25 doping levels. The experimental and theoretical measurements abstracted the stretch of lattice parameters, i.e., the crystallographic axis and the lattice cell volume, and the dislocation of the crystallographic plane (1 1 4) for the hexagonal system, certified the heavy Y3+-Ni3+ ions substitution. To examine the morphological parameters, FESEM presented the regular hexagonal platelets of sizes ~ 1–2 μm, and EDX revealed the presence of constituent elements with their atomic and weight percentages in SrFeYNiO products. The extraction of vibrational frequencies of Fe–O bonds at tetrahedral and octahedral sites of iron through FT-IR spectroscopy authenticates the formation of the SrM phase. XPS correlated the doped elements, i.e., nickel in Ni+2 and Ni+3 and yttrium in Y+3, whereas parent element, i.e., iron in Fe+3 and Fe+2 chemical states, enlightened their impact on the magnetic parameters. Hysteresis loop analysis deduced a linear decline in magnetic parameters such as saturation magnetization (Ms) and remnant magnetization (Mr) due to non-magnetic Y3+ and less magnetic Ni3+ ions installment in 4f1 and 2b polyhedral sites of Fe3+ ions. However, high coercivity (Hc) up to 2.92 kOe ∈ x = 0.15 and extended magnetocrystalline anisotropy (MCA) up to 5.790× 106 Erg/g ∈ x = 0.15 of our obtained ceramic magnets affirmed their application in permanent magnetic industry. M(T) curves also demonstrated the decrease in Ms and displayed an SPM at TB, which is shifting towards lower temperatures with increasing Y3+-Ni3+ contents approved the expansion of lattice parameters.