Enhanced bidirectional variable modulus property in NdFeB-based MREs via magnetocrystalline anisotropic and optimized particle distribution

Magnetic field-assisted manufacturing of groove-structured flexible actuators with enhanced performance

We investigate the effects of B2O3 addition on structural and magnetic properties of hard magnetic BaFe12O19 particles. The conventional solid state reaction method is used as the synthesis route. Single phase BaFe12O19 could be synthesized with very small amounts of B2O3 addition and with calcination at low temperatures (850° C) in short times (1 h). B2O3 addition also improves the magnetic parameters significantly. Remanence magnetization and specific magnetization at 1.5 T increase by ∼40% in magnitude although no significant variations on coercivity is observed.

A microstructure enhancement method for hard magnetic particle chains based on magnetic field oscillation sieve

In this paper, we introduce our developed magnetically actuated artificial tentacles. Tentacles are found in nature, for example, in cuttlefish, octopus, and jellyfish. These natural tentacles have flexibility without skeletons or joints and can move in complex ways. In the present work, we propose an actuation system for the complicated motion of the tentacles and developed a method to fabricate an artificial tentacle composed of a silicone elastomer and hard magnetic particles. The present tentacles could be actuated and controlled by an applied rotating magnetic field. A 2-dimensional simulation system was also developed to predict the motion of the artificial tentacles. The simulated results showed good agreement with experimental data. Finally, an artificial tentacle was prepared to show that the tip of the structure was controlled to draw some motion. A periodic circular motion was demonstrated as an example.

Inspired by ciliate microorganisms such as Paramecium, this study designs and optimizes a cilia-driven magnetic soft robot based on gradient magnetization. The robot is primarily composed of a non-magnetic body and magnetic ciliary legs embedded with hard magnetic particles, aiming to achieve efficient and controllable locomotion. Finite element simulation was employed to systematically analyze the influence of external magnetic field parameters and the connection method of the hinge-like structure on the robot's leg deformation and locomotion efficiency. Through experimental optimization of the driving magnetic field parameters, the optimal driving conditions were determined to be <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$7 \text{mT}, 20 \text{Hz}$</tex>, and a duty cycle of 0.6, under which the robot's locomotion speed increased by approximately 40%. Furthermore, trajectory planning experiments verified that the robot can achieve stable and controllable movement at the air-liquid interface under these optimized conditions, with a mean trajectory tracking error of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$429.8 \pm 289.2 \mu \mathrm{m}$</tex>. This demonstrates the effectiveness of the structural optimization and magnetic field control methods.

A new approach of data recording during manufacturing is to store information directly on machine components. This way, the components may serve as their own information carrier throughout the whole manufacturing process, and later in the working cycle. Such a concept is called “gentelligent” (for genetically intelligent) and aims at allowing to inherit fabrication and application data to the product's next generation. This requires a new kind of machine parts, which are capable for collecting, preprocessing, and storing information (e.g. temperature and forces during use of the component) on their surface. For storing the required information, proven principles of the peripheral magnetic data recording including inductive writing and a magneto‐optical readout are applied. The storage medium used is a material developed recently: “magnetic magnesium”, i.e. magnesium filled with hard magnetic particles. To allow a magneto‐optical readout based on the Magneto‐optical Kerr Effect (MOKE), bulk material is covered with a soft magnetic layer, called a keeper layer. The keeper layer is supplied to generate a homogeneous magnetic and reflective surface which is not provided by pure “magnetic magnesium”. This paper describes the development of the recording system. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

In the contemporary era, novel manufacturing technologies like additive manufacturing (AM) have revolutionized the different engineering sectors including biomedical, aerospace, electronics, etc. Four-dimensional (4D) printing aka AM of smart materials is gaining popularity among the scientific community, which has the excellent ability to make soft structures such as soft robots, actuators, and grippers. These soft structures are developed by applying various stimuli such as pH, temperature, magnetic field, and many combinations onto soft materials. Stimuli in 3D printing permit various shape-morphing behaviors such as bending, twisting, folding, swelling, rolling, shrinking, origami, or locomotion. A wide variety of soft magnetic structures can be fabricated through the incorporation of soft or hard magnetic particles into soft materials resulting in magneto-active soft materials (MASMs). With this integration, magneto-thermal coupling actuation allows diverse magneto-deformations, facilitating the development of personalized devices that are capable of enhanced deformation. In this review, guidelines are provided on the 3D printing for MASMs such as magneto-active polymers (MAPs), magneto-active composites, and magneto-active hydrogels (MAHs) on the booming development of various smart and flexible devices such as soft robots, wearable electronics, and biomimetic devices. Moreover, 3D-printed soft robotics have an outstanding capacity to adapt to complicated situations for many advanced actuating applications. Finally, some current challenges and emerging areas in this exciting technology have been proposed. Lastly, it is anticipated that technological advancements in developing smart and intelligent magneto-active structures will have a significant impact on the design of real-world applications.

A new approach on tracking components throughout the entire manufacturing processes is to apply magnetic recording technology to storing key production data on the component itself. The system investigated uses magnetic magnesium , i.e. a magnesium matrix filled with hard magnetic particles. For storing the data, a classic inductive write head, consisting of a soft magnetic ring core with a write gap in the flux path and a coil for creating the magnetic flux is chosen. For an application in a machine environment, readout has to be done at a distance. On approach of such non-contact readout, an advantage of the Magneto-Optical Kerr Effect (MOKE), which senses the direction of magnetization of a reflecting surface, is to be taken. As in the case of data storage, information is encoded in the magnetization pattern of data tracks.

Exploring the effect of exchange coupling in (SrFe9.8Al2La0.2O19)1-x/(Co0.7Zn0.3Fe2O4)x nanocomposites synthesised by sol–gel auto combustion method

9 - Textile fabrics and ferrite-loaded composite materials for electromagnetic-shielding applications

Two-dimensional Monte Carlo simulations of a suspension comprised of magnetic and nonmagnetic particles in gradient magnetic fields

Microbial activity plays a major role in the sedimentary iron cycle. Some microbes gain energy by reducing or oxidizing iron and thus induce changes in the sedimentary iron mineral assemblage. Magnetotactic bacteria engage in controlled, intracellular precipitation of magnetic iron minerals. These biological transformations are frequently a major influence on the magnetic properties of sediments. Understanding the biogeochemical iron cycle therefore facilitates the interpretation of sedimentary paleomagnetism; conversely, magnetic tools provide a non-destructive and rapid way of analyzing the biogeochemical iron cycle in modern and ancient environments. Ferromagnetic resonance (FMR) spectroscopy, a form of microwave spectroscopy, provides a rapid means of assessing internal fields generated in magnetic particles by interparticle interactions and particle anisotropy. It can therefore assess particle shape, arrangement, and heterogeneity. Because magnetotactic bacteria typically produce chains of crystals with narrow distributions of size and shape, FMR spectroscopy is well suited as a screening tool for identifying fossil magnetotactic bacteria (magnetofossils). Application of FMR and other techniques to modern carbonate sediments of the Triple Goose Creek region, Andros Island, Bahamas, reveals the contributions of magnetotactic bacteria, iron metabolizing bacteria, and sulfate reducing bacteria to the magnetization of carbonate sediments. In sediments above mean tide level, magnetofossils dominate sediment magnetism. Although stable remanent magnetization is preserved throughout the sediments, the quantity of biological magnetite diminishes by an order of magnitude in the iron reduction zone. Below this zone, the development of a sulfate reduction interval can lead to the authigenesis of magnetic iron sulfides. Supratidal portions of shallowing-upward parasequences in carbonate rocks therefore likely provide the most accurate record of syndepositional paleomagnetism. Anomalous magnetic properties of clay deposited in the Atlantic Coastal Plain, New Jersey, during the Paleocene/Eocene Thermal Maximum (PETM) led previous authors to speculate that an extraterrestrial impact triggered the PETM. Reexamination of the clay using FMR and transmission electron microscopy reveals instead that the clay hosts abundant magnetofossils. The first identification of ancient biogenic magnetite using FMR indicates that the anomalous magnetic properties of PETM sediments were not produced by an impact, but instead reflect paleoenvironmental changes along the western North Atlantic margin.

Industrial and vehicular emissions of particles cause multiple damages to human health due to concentration, size, and composition. These emissions contain magnetic particles; therefore, low-cost properties allow tracking and monitoring them. This study is aimed at identifying the primary sources of magnetic material in 100 samples of urban road dust from San Luis Potosi, Mexico, analyzing the influence of land use and the type of road on these particles. Magnetic susceptibility (χlf) and isothermal remanent magnetization at 0.7 T (IRM0.7T) were determined, as well as the iron and manganese content using X-ray fluorescence. The distribution of particles was examined by land use and type of road through geostatistical maps and variance analysis. The results showed that the iron and manganese content, χlf, and IRM0.7T were positively correlated, indicating a possible common origin. The primary sources identified were the iron smelter and laminator in the industrial park. Urban land use influenced the content of iron, manganese, and magnetic material in urban road dust. The land uses with the more significant transformation (industrial and mixed) presented the highest values of iron, manganese, χlf, and IRM0.7T. On the other hand, vehicular traffic was indirectly assessed through the type of road, influencing the magnetic signal of urban road dust and finding the highest signals in primary and secondary roads. Then, the magnetic properties allowed the tracking and monitoring of magnetic particles from industrial and vehicle emissions.

Magnetic elastomers are one of the most important types of magnetoresponsive materials. They are characterized by large changes in their shape and rehological properties as a response to external magnetic fields [1]. Similarly to magnetic fluids and gels, these are hybrid materials that consist of magnetic nano- or microparticles embedded in a magnetically passive carrier material. Magnetic elastomers are candidate materials for many technological applications, like adaptive damping devices, vibrational absorbers, stiffness tunable mounts, soft actuators and micromanipulators, force sensors or artificial muscles, see [2] and references therein. Here, we study theoretically a novel microstructural design for a hybrid magnetic elastomer material that has been synthesized for the first time very recently [3-5]. This design is based on the embedding within the polymer matrix of two types of magnetic particles in different amounts: a low volume fraction of magnetically hard (MH) colloidal particles---typically, ferromagnetic particles of 5-100μm of diameter---and a high volume fraction of smaller, magnetically soft (MS) particles---paramagnetic particles with a diameter typically smaller than 5μm. We study the response of this hybrid magnetic material to external magnetic fields by means of two theoretical approaches. First, we perform extensive computer simulations with a bead-spring model of the system that takes into account the magnetic influence of the MH particles on the MS ones, as well as the mechanical coupling imposed by the polymer matrix on the rearrangements of the particles [6]. Finally, we compare the results obtained from this approach with the ones provided by a continuous magnetomechanical model. In both approaches we focus on a minimal representative volume of the material, consisting of a single MH particle surrounded by a cloud of MS ones and the mechanical coupling between all of them. We analyze the deformations of this elementary volume as a response to the external fields.

Design of magnetic elastomer composites with tunable magnetic responses from soft to hard magnetization