Magnetic Materials

Development of mechatronic systems depend strongly on development of magnetic materials. It applies to soft and hard magnetic materials. Development of magnetic materials gives the designers of electric machines and other electromagnetic transducers new opportunities to design electric machines with better operational parameters, and also often allows to reduce manufacturing cost. Magnetic materials of more and more application in electric motors and other electromagnetic transducers are magnetic materials in the form of powder. Materials in a form of powder and powder metallurgy create new possibility for preparing new generation of magnetic materials and in consequence new generation of magnetic circuits. Application of powder metallurgy has many advantages, such as i.a. low losses of material, low consumption of labor and energy, and resulting low unit cost of products. Powder magnetic materials can be obtained by various methods, and used in elements produced by a variety of methods. Such elements may be produced by means of sintering or bonding with plastic. Advanced polymeric materials and nanocomposites are the most suitable for such demanding applications. Particularly the latter method has many advantages due to simpler technology, as the process require lower temperatures, without protective atmosphere. One of the basic advantages of this technology is ability to shape their physical properties to expectation designers of electric machines, traducers and whole mechatronic systems. Magnetic elements are to meet many different requirements, depending on their construction, purpose or working environmental. In one case it may be important to obtain maximum value of magnetic parameters, in other case mechanic or electric properties may be equally important. Additional strength of that technology is ability to manufacture magnetic elements of complex shapes and high dimensional precision, without additional machining. Technology of manufacturing elements of hard and soft magnetic powders is very similar, whereas parameters of powder bonding process depend on selected magnetic powder and bonding material. The process of manufacturing magnetic elements with powder binding method consists in pressing and than hardening the moulding. Properties of materials depend in a first stage on powder material composition and structure and in the second stage on technology of preparing elements from materials. The magnetic properties of these composites depend mainly on the magnetic properties of the powder particles, their shape and their size distribution in the dielectric matrix. The mechanical properties of magnetic elements depend mainly on kind and quantity of the binder. The resin surrounded grain of powder changes resistivity of elements. The resin not only bonds grain but in the same time has a role of isolation each grain. Thermal properties of magnetic elements depend mainly on the type of magnetic powder. Physical properties of course depend on technology and parameters of the process. There are two main methods for preparing magnetic elements by bonding grain of powder by resin: injection molding and compression molding. By changing parameters of these two processes we can tailor physical properties of magnetic elements. From application point of view very important virtue of such technology is the possibility of tailoring physical properties of the magnetic resin-bonded elements, to fulfill exactly the expectation of the electric machines designer. Properties of magnetic circuits depend mainly on the properties of soft and hard magnetic elements, their magnetic parameters, shape, size and also type of magnetization.

The change of properties of one of this elements results in changes of properties of magnetic circuit. There are few different methods for tailoring properties of soft and hard magnetic elements and in consequence properties of magnetic circuit: - technology of production and its parameters, - admixture basic magnetic powder by another kind of powder, - preparing permanent magnets with pole shoes made of magnetically soft powder material - changing the shape and dimension of elements. We have to know how composition, parameters of technology processes influence on properties of magnetic elements and than on properties of magnetic circuits. This knowledge is necessary to design new generation of magnetic circuit. Physical properties of materials change with changes of temperature. Magnetic elements work in different temperature. It is indispensable to know how physical properties of these elements change with changes of temperature. We plan to measure physical properties in the range of temperature from 40oC to + 100oC: magnetic, mechanical (compression strength, bending strength, tensile strength), electric, thermal properties. Very important are knowledge about behavior of magnetic materials for magnetic circuit in different surrounding. Mechatronic systems with elements from magnetic powders work in different condition: different temperature, different humidity, changes of temperature or humidity. Aging of magnetic materials has a influence on a length of a life time of machines. Magnetic circuit is a part of machines and mechatronic systems and the length of the life time of this elements influence on a length of a life time whole system. The knowledge about resistance to different environmental factor allows choosing a right materials for specific application as designer of magnetic circuit require. It is the reason that climatic and aging investigations have to be done. Magnetic materials of more and more application are hard magnetic powders from melt-spun ribbon Nd-Fe-B and soft magnetic powders of iron. This kind of magnetic materials will be used in the project. Nd-Fe-B bonded magnets are prepared from the melt-spun ribbon from the Nd-Fe-B alloys. The method of melt-spinning allow to produce ribbon with diameter of grain in a range 60100nm. The powder from this ribbon allow prepare permanent magnets with good properties better than utilized ferrite magnets and prepare by technology more easy than sintering technology. The technology of manufacturing this kind of permanent magnets makes it possible to produce magnets with different physical properties by using mixture of powders. This affects the magnetic properties as well as mechanical and thermal properties. This kind of permanent magnets with isotropic characteristic can be later magnetized along whichever direction. It is also possible the multi-pole magnetizing with configuration of magnetic pole adjusted to the design and layout of electric motor. Improvements in magnetic materials refer also to magnetically-soft materials. The sheet structure of magnetic core has been used for designs of electric machines since the beginning of the 19th century. Nowadays the magnetic core with sheet structure is more frequently substituted by a core of powder composite magnetic materials. The magnetic core made of powder magnetic material present number of advantages. Magnetic core executed in soft magnetic powder composite allows three dimensional distribution of magnetic flux in magnetic core. This extend the scope of design solutions and allows full adaptation to magnetic core profile. The strength of such magnetic cores is ability to obtain complex shapes and shaping their physical properties as for powder hard magnetic elements. Presence of

dielectric, which acts as a binding and insulating agent, reduces losses due to eddy currents. Thermal isotropy and good thermal conductivity improves dissipation of heat from external surface. Magnetic properties of hard and soft magnetic elements of course are a main factor deciding about their application, but in many applications very important are mechanical properties. The main factor deciding about mechanical properties of magnetic elements and their changes in different environments are type of resin used as a bonding agent. The resistance of the applied bonding plastic is very important for many application too. In our investigation we plan to use different type of bonding agent, between others, hybrid polymeric systems and new generation of nanocomposite bonding agent. Designing of the architecture of hybrid systems is the modern method to achieve novel polymeric materials, specifically applied as binders for advanced coatings. Hybrid polymeric systems to be synthesised will include: grafted and block copolymers of specific architecture based on silicones, polyurethanes, polyesters and epoxies. The characterisation of the investigated systems will be made by using modern analytical methods such as: FTIR ATR, 1 HNMR,13CNMR, 29SiNMR, DSC and TGA. The expected technical benefit will be the improvement of properties of the investigated hybrid systems as compared to the individual polymers due to synergism. The expected scientific benefit will be understanding of the influence of polymer system architecture on the macro-properties of the resulting magnetic circuits what will enable to develop products tailored for these sophisticated applications. The development of novel hybrid polymeric systems based on existing starting materials and production potential will contribute to preservation of the environment and the minimum use of natural resources what is one of the important European Community social objectives. The extending of the range of applications of novel hybrid polymeric systems will contribute to improvement of high-technologies thus leading to better quality of life and health and improved safety (including the working conditions as the low VOC and waterborne systems, powder coatings and high solids are applied). Application of new generation of nanocomposite bonding agents focused on magnetic circuits for special applications will give very important impact to the planned results of this project. Nanocomposites containing strategically functionalized spherical nanosilica built-in the polymer matrix exhibit excellent mechanical, weathering and anti-aiging properties up to 70% higher as compared to the properties of basic polymers not containing nanoparticles. Additional advantage using powder metallurgy for magnetic circuit is possibility preparing layer magnetic elements, with soft and hart magnetic layer, in one process. Nowadays very important feature of materials are their utilization and possibility of recycling. The investigation on this field are foresee in the project. Application of hybrid polymeric systems and nanocomposites give very important opportunity for easy recycling of used magnetic circuits. The following most important recycling methodologies are planned to be studied within the project: reactive polymer processing and depolymerization process of silicone-containing hybrid systems and nanocomposites. Both proposed recycling strategies offer the possibility of nanoparticles recycling together with polymer matrix. It is very important from toxicological point of view connected with mostly not-defined toxicity of nanoparticles. Knowledge about properties of powder magnetic materials, powder magnetic elements and relation between technologies, composition, changes of parameters with temperature etc. allow to prepare magnetic circuit exactly for designer requirements. Powder metallurgy is a good tool for designer of new generation mechatronic systems.