Rapid Characterization Method for SMC Materials for a Preliminary Selection

In electrical machines, laminated steels are commonly adopted as soft magnetic materials, while for permanent magnets, sintered ferrites and NdFeB are the most common solutions. On the other hand, the growing demand for volume reduction with the increment of efficiency leads to the necessity of exploring other magnetic materials able to face the challenge better than the traditional ones. Bonded magnets have been used to replace sintered magnets, obtaining a better use of space and particular magnetic properties. Instead, for the magnetic circuit, Soft Magnetic Composites (SMC) allow realizing very complex magnetic design (3D path for flux) with iron loss reduction at medium-high frequencies, especially for the eddy currents loss contribution. On the other hand, SMC materials have such drawbacks as low mechanical properties and high hysteresis losses. For this reason, in this work, different studies considering several variables have been carried out. SMCs were produced through a moulding process; inorganic and organic layers to cover ferromagnetic particles were used, adopting different coating processes. Particular tests have been performed for a quicker and more indicative overview of the materials obtained. The single sheet tester (SST) is easier than traditional toroidal methods; on the other hand, the multiplicity of variables affects the SMC materials and their process. For this reason, coercivity and conductibility tests permit rapid measurement and provide a direct classification of the produced SMCs, providing the main information needed to select suitable materials. Results highlighted that choosing the more appropriate SMC material is possible after using these simple preliminary tests. After these tests, it was possible to argue that with 0.2 wt% of phenolic resin as the organic layer (and compaction pressure of 800 MPa), it is possible to produce a good SMC. On the other hand, the SMC with 0.2 wt% of epoxy resin (and compaction pressure of 800 MPa) gives a minor coercivity value. Additionally, despite the SMC with the inorganic layer, 0.2 wt% of nano-ferrites showing the best coercivity values (specifically for vacuum treatment at 600 °C), their resistivity was unsatisfactory.

LABORATORY STUDIES OF PROPERTIES OF SOFT MAGNETIC POWDER COMPOSITE MATERIALS

Изучение эффективности использования электротехнических материалов является актуальной проблемой в области изготовления электрических машин. Одним из важнейших аспектов изготовления электрических машин является проектирование магнитной системы машины. В качестве магнитной системы используют магнитопроводы из различных магнитомягких материалов. Эти материалы отличаются магнитной проницаемостью и удельными магнитными потерями. Данные параметры материалов влияют на нагрев, размер, стоимость и эффективность электрической машины. В целях экономии экспериментальная оценка параметров магнитомягких материалов производится на заготовках различных форм и размеров, на специальных измерительных стендах, согласно международным энергетическим стандартам. В данной статье предлагается экспериментальная установка для лабораторных исследований магнитных свойств магнитомягких материалов, методом кольцевых заготовок, в соответствие со стандартом МЭК-60404-6. В составе установки используется только стандартное недорогое оборудование. Необходимый коэффициент формы магнитной индукциидостигается последовательной коррекциейнапряжения вторичной обмотки с помощью цифрового регулятора. Подход к программной реализации алгоритма последовательной коррекции напряжения вторичной обмотки изложен в статье. С помощью предлагаемой установки проведено исследование свойств образца из магнитомягкого композиционного порошкового материала Somaloy 700-3p (800 MPa) и сравнение результатов с каталожными данными производителя. По итогам работы выявлено, что с помощью предлагаемойустановки могут производитьсяизмерения свойств магнитомягких материалов, в соответствие со стандартом МЭК-60404-6 с необходимой точностью. Предлагаемая установка может быть использована как в качестве учебного стенда, так и в качестве измерительной установки для идентификации свойств магнитомягких материалов при проектировании электрических машин. The study of the efficiency of using electrical materials is of great interest in the field of manufacturing electrical machines. One of the most important aspects of the manufacture of electrical machines is the design of the magnetic cores of the machine. Magnetic cores made of various magnetically soft materials are used as a magnetic system. These materials differ in magnetic permeability and specific magnetic losses. These material parameters affect the heating, size, cost and efficiency of electric machines. In order to reduce expenses, the experimental evaluation of the parameters of soft magnetic materials is carried out on samples of various shapes and sizes, on special experimental setups, in accordance with international electrotechnical standards. This article proposes an experimental setup for laboratory studies of the magnetic properties of soft magnetic materials by the method of ring specimens, in accordance with the IEC-60404-6 standard. The setup uses only standard inexpensive equipment. The required shape factor of the magnetic flux density is achieved by sequential correction of the secondary winding voltage using a digital regulator. The approach to the software implementation of the algorithm for sequential correction of the secondary winding voltage is described in the article. The proposed experimental setup was used to study the properties of a sample made of a soft magnetic composite powder material Somaloy 700-3p (800 MPa) and compare the results with the manufacturer's catalog data. Based on the results of the work, it was revealed that the proposed setup can be used to measure the properties of soft magnetic materials in accordance with the IEC-60404-6 standard with the required accuracy. The proposed experimental setup can be used both as a training stand and as a measuring installation for identifying the properties of soft magnetic materials in the design of electrical machines.

Microwave Absorption Properties of Fe40Co60 Based Nanocomposites

Microwave absorbing materials are applied in stealth, communications and information processing technologies. This kind of material dissipates an electromagnetic wave by converting it into thermal energy. The nanostructuration of materials became a reliable route over the years to enhance the dielectric and magnetic properties, which induce the required interaction. Nanostructured Fe-Co alloys are soft magnetic materials that make them promising candidates for microwave absorption when combined with other materials. The aim of our study was therefore to investigate the microwave absorption properties of based nanocomposites. The nanocomposites were obtained by the solution dispersion method. Nanocrystalline alloys elaborated by mechanical alloying (MA) in a high-energy planetary ball mill (RETSCH PM400) were dispersed into commercial epoxy resin matrix to form thin polymer nanocomposites. The grain size refinement and structural properties changes during milling process were characterized using powder’s X-ray Diffraction (XPERT PRO MPD diffractometer) at different milling durations. XRD spectra analysis show that a grain size refinement of 4.54 nm was reached after 60h milling accompanied with 1.2 % microdeformations. Obtained powders were shaped in small discs for which resonant cavity measurements were undertaken. The based nanocomposites have been subject to an experiment of two-port S parameters measurement in a rectangular waveguide (R120). The microwave experiments involved a Network Analyzer (VNA). Obtained results in terms of reflection losses show a good absorbing characteristic over the [8-15] GHz microwaves band.

Estimation of Energy Losses in Nanocrystalline FINEMET Alloys Working at High Frequency

Soft magnetic materials are at the core of electromagnetic devices. Planar transformers are essential pieces of equipment working at high frequency. Usually, their magnetic core is made of various types of ferrites or iron-based alloys. An upcoming alternative might be the replacement the ferrites with FINEMET-type alloys, of nominal composition of Fe73.5Si13.5B9Cu3Nb1 (at. %). FINEMET is a nanocrystalline material exhibiting excellent magnetic properties at high frequencies, a soft magnetic alloy that has been in the focus of interest in the last years thanks to its high saturation magnetization, high permeability, and low core loss. Here, we present and discuss the measured and modelled properties of this material. Owing to the limits of the experimental set-up, an estimate of the total magnetic losses within this magnetic material is made, for values greater than the measurement limits of the magnetic flux density and frequency, with reasonable results for potential applications of FINMET-type alloys and thin films in high frequency planar transformer cores.

A mechanically strong and ductile soft magnet with ultralow coercivity

Soft magnetic materials (SMMs) are indispensable components in electrified applications and sustainable energy supply, allowing permanent magnetic flux variations in response to high frequency changes of the applied magnetic field, at lowest possible energy loss1. The global trend towards electrification of transport, households and manufacturing leads to a massive increase in energy consumption due to hysteresis losses2. Therefore, minimizing coercivity, which scales the losses in SMMs, is crucial3. Yet, meeting this target alone is not enough: SMMs used for instance in vehicles and planes must withstand severe mechanical loads, i.e., the alloys need high strength and ductility4. This is a fundamental design challenge, as most methods that enhance strength introduce stress fields that can pin magnetic domains, thus increasing coercivity and hysteretic losses5. Here, we introduce a new approach to overcome this dilemma. We have designed a Fe-Co-Ni-Ta-Al multicomponent alloy with ferromagnetic matrix and paramagnetic coherent nanoparticles of well-controlled size (~91 nm) and high volume fraction (55%). They impede dislocation motion, enhancing strength and ductility. Yet, their small size, low coherency stress and small magnetostatic energy create an interaction volume below the magnetic domain wall width, leading to minimal domain wall pinning, thus maintaining the material’s soft magnetic properties. The new material exhibits an excellent combination of mechanical and magnetic properties outperforming other multicomponent alloys and conventional SMMs. It has a tensile strength of ~1336 MPa at 54% tensile elongation, an extremely low coercivity of ~78 A/m (<1 Oe) and a saturation magnetization of ~100 Am2/kg. The work opens new perspectives on developing magnetically soft and mechanically strong and ductile materials for the sustainable electrification of industry and society.

Effect of Fe-Ni Substitution in FeNiSiB Soft Magnetic Alloys Produced by Melt Spinning

Alloys of FeNiSiB soft magnetic materials containing variable Fe and Ni contents (wt.%) have been produced by melt spinning method, a kind of rapid solidification technique. The magnetic and structural properties of FeNiSiB alloys with soft magnetic properties were investigated by increasing the Fe ratio. X-ray diffraction analysis and SEM images shows that the produced alloy ribbons generally have an amorphous structure, together with also partially nanocrystalline regions. It was observed that the structure became much more amorphous together with increasing Fe content in the composition. Among the alloy ribbons, the highest saturation magnetization was obtained as 0.6 emu/g in the specimen with 50 wt.% Fe. In addition, the highest Curie temperature was observed in the sample containing 46 wt.% Fe.

Metrological aspects of an automated method for measuring electrophysical parameters of soft magnetic materials

The structure of an automated system for measuring magnetic-hysteresis loops, normal magnetization curve, magnetic permeability with an error of no more than ± 1% is proposed. The measuring principle is based on the inferential measurements of the magnetic induction and the coercive force by integrating the secondary voltage and the excitation current. As a result of metrological analysis, an increase in the measurements accuracy is achieved both by improving the hardware implementation and calibrating the measuring channels, by introducing a correction for the systematic component of the error.

Application of high-entropy alloys

From accumulated information on structure, properties, stability, and methods of manufacturing the high-entropy alloys (HEA) created early in the 21 century it follows that they possess a whole complex of useful properties that suggests their perspective application in different branches of industry. The authors have made a short review of scientific articles on analysis of possibilities of HEA application in specific science-consuming branches of the last 5 years. In biomedicine the protective coatings made of (TiZrNbHfTa)N and (TiZrNbHfTa)O HEAs possess biocompatibility, high level of mechanical properties, high wear- and corrosion resistance in physiological media, and excellent adhesion. Products made of (MoTa)χNbTiZr passed clinical tests successfully when being implanted to living muscular tissue. The developed HEAs based on rare-earth elements and metals of Fe group such as YbTbDyAlMe (Me = Fe, Co, Ni) possess magnetocaloric effect, have Curie temperature close to room one and may be used in modern refrigerator mechanisms. Changing in stoichiometric composition of CoCrFeNiTi HEAs, alloying them and performing thermal treatment, the researchers succeed in obtaining soft magnetic materials. Fields of HEA application are presented as following: catalysts of ammonia oxidation - (PtPdRhRuCe), ammonia decomposition - (RuRhCoNiIr), oxidation of aromatic alcohols - (Co0,2Ni0,2Cu0,2Mg0,2Zn0,2 ), electric catalysts of hydrogen extraction - (Ni20Fe20Mo10Cr15Co35 ), redox reactions (AlCuNiPtMn and AlNiCuPtPdAu), and oxidation of methanol/ethanol. HEAs can be used as electrodes - anodes and cathodes for Li-ion and Na-ion accumulators. Synthesized nanoporous HEA AlCoCrFeNi has high bulk density up to 700 F/cm3 and cyclic stability (>3000 cycles) and is used in supercapacitors. High-entropy oxides such as (MgNiCoCuZn)0.95Li0.05O with high dielectric properties in a wide frequency range may be used in electronic converters. Examples of HEA application are given: as coatings of ship parts being operated in sea water, various welded joints, parts of nuclear reactors. Perspectives of widening the fields of HEA application are indicated.