Marcelo Rubén Pagnola
Argentina INTECIN (UBA-CONICET)
Published in 2018
- Influence of Nb, Mo, and Ti as doping metals on structure and magnetic response in NdFeB based melt spun ribbons
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NEFEBmagnetic propertiesNb-Mo-Ti dopantsEnergy Product - Authors: D. Derewnicka-Krawczyńska; S. Ferrari; V. Bilovol; M. Pagnola; K. Morawiec; F. D. Saccone
- Journal: Journal of Magnetism and Magnetic Materials
- Description:
- In this work, it is shown a comparative analysis of magnetic measurements that has been done over rapidly quenched melt-spinning alloyed ribbons with the formula NdyFe(86−y−x)B14Mx (X = 2, 4; Y = 7,8; M = Nb, Mo, Ti). The magnetic properties such as coercivity, saturation magnetization and energy product (B.H)max are analyzed for ribbons annealed for 20 min at 953 K in each case. It is observed that the sample with the highest saturation isNd7Fe77B14Mo2 (∼1400 kA.m−1) while the sample Nd8Fe74B14Nb4 has the lowest saturation value (∼600 kA.m−1). The sample Nd7Fe75B14Ti4 exhibits the lowest value (∼400 kA.m−1) while the Nd8Fe74B14Ti4 exhibits the highest value (∼700 kA.m−1) and the maximum (B.H)max value ∼110 kJ.m−3. The use of different experimental techniques, such as X-ray diffraction, Mössbauer spectroscopy, X-ray photoelectron spectroscopy, helped us to comprehend how M doping has influenced in a broad set of physical and chemical properties (e.g. crystalline phases, grain boundary doping enrichment, etc.) and how they correlate with the various observed magnetic features for these ribbons.
Published in 2016
- Biot number behaviour in the Chill Block Melt Spinning (CBMS) process
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BIOT NUMBERCBMSOPEN FOAMMELT SPINNING - Authors: M.Pagnola; M.Malmoria; M.Barone
- Journal: Applied Thermal Engineering
- Description:
- This paper shows the change obtained in the Biot number (Bi) during the adhesion interface and the contact between phases, where the cooling and solidification of the ribbon obtained by the CBMS process occurs. This change shows an increase in the number of Bi according to the tangential velocity of the copper wheel (Vx) in the pressure range of the tests that define the ejection speeds in the nozzle (Vo). The present study demonstrates that a zone where Vo is close to 2 m/s appears, and a transition of the Bis/l numbers from magnitudes below unity until this value is exceeded can be observed. In this study, the Bis/l > 1 values indicate that Newtonian cooling occurs during the ribbon’s solidification process and show that the convective forces on the external part of the solidifying mass begin to influence the amount of heat transferred during the liquid/solid phase in the adhesion zone.
Published in 2015
- Influence of z/w relation in Chill Block Melt Spinning (CBMS) process and analysis of thickness in ribbons
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SOLIDIFICATIONMAGNETIC MATERIALS2D MODELINGTHIN FILMS - Authors: Marcelo R. Pagnola; Marcelo Barone; Mariano Malmoria; Hugo Sirkin
- Journal: Multidiscipline Modeling in Materials and Structures
- Description:
- The purpose of this paper is to present an analysis over own and other authors data related to the process of Chill Block Melt Spinning (CBMS) and propose a model of analysis for interpretation. The similarity between our own experimental data. with others data reported by other authors, both z/w ratio and the thicknesses of the films produced has been found. This allows us to establish an exponential decay of the parameters studied and possibly link it to the Newtonian cooling to which the samples are subjected in its production.
Published in 2014
- Analysis of Fe78Si9B13 (%at.) ribbons of noncommercial scrap materials produced by melt spinning equipment
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AMORPHOUS MATERIALSMAGNETIC MATERIALSMOSSBAUER EFFECTNANOSTRUCTURES - Authors: Marcelo R. Pagnola; Mariano Malmoria; Marcelo Barone; Hugo Sirkin
- Journal: Multidiscipline Modeling in Materials and Structures
- Description:
- The purpose of this paper is to present a ribbons production route of composition Fe78Si9B13 (%at.) using low-cost noncommercial scrap materials to obtain usable magnetic cores by melt spinning technique and their characterization. This way, these may compete with the materials produced by conventional casting processes. The methodology is to design a master alloy with scrap different starting compositions, to which Fe is added to get the desired atomic ratio of components. With this starting alloy, using the method of melt spinning, in its variant of chill block melt spinning, are achieved amorphous ribbons with desired soft magnetic behavior. Then these ribbons are thermally treated for achieving nanocrystalline structures to improve the performance in the magnetic cores.
Published in 2009
- Improvement to the second‐order rational functions approximation for hysteresis cycles of magnetic materials
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Hysteresis CyclesMagnetic MeasurementPhysical PropertiesSemi‐empirical Approach - Authors: M.R. Pagnola; F. D. Saccone; A. Ozols; H. Sirkin
- Journal: COMPEL
- Description:
- The purpose of this paper is to introduce a simplified method, based on an improvement to the actual second‐order approximation to magnetic hysteresis curves, to calculate an estimation of quasi‐static hysteresis loops of ferromagnetic materials. The addition of a new dB(B) function is proposed to second‐order rational approximation for the upward and downward magnetic quasi‐static hysteresis loop. The new semi‐empirical approach is tested with typical cycles of commercial Ni‐ferrites (ferroxcube) and Ni standards using a vibrating sample magnetometer (VSM). The model is simple and a fast tool to reproduce with reasonable accuracy the hysteresis loops based on appropriate parameters of materials under analysis. The proposed extension to the Rivas model has reduced the maximum difference between experimental and modeled values from 19 to 0.08 per cent in the approximation to different hysteresis cycles of the magnetic materials studied here.
Published in 2009
- Nanocrystals magnetic contribution to FINEMET-type soft magnetic materials with Ge addition
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FINEMETNanocrystalsGe additionStructural Properties - Authors: D. Muraca; J. Silveyra; M. Pagnola; V. Cremaschi
- Journal: Journal of Magnetism and Magnetic Materials
- Description:
- Over the last years several works have been published in which magnetic and structural properties of soft magnetic nanocrystalline alloys were reported. Among these, there are a series of articles where the nanocrystals composition of FINEMET-type alloys with Ge addition was obtained by Mössbauer spectroscopy (MS) and X-ray diffraction (XRD). By considering a linear relationship between the magnetic moments of the nanocrystals and the composition of various elements in these crystallites, the magnetic moment of the nanocrystals was calculated. This paper reviews results obtained by different authors since 1980 and they are compared with ours. In turn, we revised some elements not previously considered for the calculus of the nanocrystals composition that allowed us to obtain the magnetic moment of the crystallites in the alloy. In particular, we analyzed FINEMET-type alloys with replacement of B for Ge: Fe73.5Si13.5Ge2B7Nb3Cu1 and Fe73.5Si13.5Ge4B5Nb3Cu1. The nanocrystalline structure was obtained by isothermal annealing of melt-spun ribbons at 823 K for 1 h. From MS and XRD we obtained the atomic composition of the nanocrystals in the magnetic material. The magnetic contribution of the nanocrystals to the alloy was calculated using a linear model and the results were compared with experimental measurements of the samples.
Published in 2006
- Electroless coating of Permalloy powder and DC-resistivity of alloy composites
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Electroless CoatingPermalloyCompositesDC-RESISTIVITY - Authors: A. Ozols; M. Pagnola; D. Iñaki García; H. Sirkin
- Journal: Surface and Coatings Technology
- Description:
- A high-resistivity coating of Permalloy (Ni–17.81Fe–1.97Mo wt.%) powders for soft magnetic composites, SMC, was developed and characterized. The coating was made using the electroless plating method employing an aqueous solution of sodium and nickel phosphates. The chemical process led to the formation of a layer up to 1 μm thick deposited on each particle surface and composed of a mixture of Ni(OH)2, P2O5 and NaPO3 compounds, as shown by X-ray photoelectron spectrometry and X-ray powder diffraction studies. The effect of coating on electrical DC resistivity was evaluated on SMC obtained mixing the metal, coated or uncoated, and thermoplastic polymer PEEK (polyetheretherketone) powders, pressing the mixture at 800 MPa and heating in air up to melting the polymer (380–410 °C). The SMC made with coated powders showed an increase in resistivity of more than two orders of magnitude compared to that obtained with uncoated powders when the polymer ranged between 0.5 and 1.5 wt.%. This difference prevails in comparison with sintered materials processed at the same pressure and sintering in hydrogen at 1350 °C. Thus, this process would restrict the eddy currents which affect the performance of soft magnetic products for AC applications.