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Amorphous and nanocrystalline Cores
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Amorphous and nanocrystalline Cores
nanoThe improvement of electromagnetic characteristics of materials used for coils manufacturing is one of important and emerged areas in modern electronics. Among such improvement methods one can note the creation of new composite materials based on soft magnetic alloys. These material are widely applied in matching, high-frequency and power transformers, as well as in current sensors and represent complicated multicomponent system. A chemical composition of soft magnetic alloys with two -phase structure is Fe73,5CuNb3Si13,5B9. Ribbons with amorphous structure characterized by the absence of a long-range order in atoms arrangement are obtained from a material melting by spinning or a flat jet methods. The melt falling from the slot of the nozzle on the rotating drum surface, is being cooled, then it solidifies, thus forming a ribbon with an amorphous structure. The ribbon's thickness is ordinary 25 ± 5 µm. In order to achieve the required magnetic properties at the second technological stage, an amorphous ribbon is thermally being treated at high temperatures. As a result of operation carried out at a temperature of not less than 600 °C, the partial crystallization occurs and nucleating centers of the iron silicide phase (α-Fe-Si) are formed.Get more news about Nanocrystalline core,you can vist our website!
Thus, a distinctive feature of such materials is the presence in their composition of both the amorphous component and a certain fraction of the crystalline phase. The crystallites size in such alloys is 10–20 nm; therefore, these materials are often called nanocrystalline. Depending on the composition of the alloy, the percentage phase ratio may vary. As a rule, the proportion of the crystalline structure prevails.
The introduction of such addings as Si and B into alloys content allows an amorphous structure forming, while niobium ions inhibit the growth of grains at higher operating temperatures. In addition to niobium ions, additives of other metals, such as Zr, Mo, Hf, Ta, W can be used to reduce crystallites size. The introduction of copper ions leads to the formation of a large number of crystallization centers.
nanoThe figure shows a schematic representation of an alloy structure with two phases.
To improve the magnetic characteristics and significantly reduce the magnetostriction, a partial removing of iron atoms with aluminum is being carried out. Moreover, due to the distribution of nanoscale crystalline granules in the amorphous matrix in such alloys: very high values of magnetic permeability, a small values of coercive force , and the saturation induction (Bs) is 0.8 ... 1.2 T (Bs) are achieved.