Additive's Structural And Magnetic Effect On The Solid State Reaction In Fe-co Powders

Résumé: The main goal of this thesis is to understand the influence of the average crystallite size as a function of the milling time on the structural, microstructural, mechanical, magnetic properties and also the growth of bacteria strains. This study is devoted to the elaboration of nanostructured Fe 15 Co 2 P 3 powder mixtures by mechanical alloying process which allows the formation of alloys with a grain size in the nanometer range, then the physicochemical characterization of the powder mixtures and also the effect of Fe 15 Co 2 P 3 powder mixtures on the growth of test bacteria. A high energy planetary ball-mill Retsch PM 400 was chosen for synthesis the powder mixtures. Phases formation, microstructural, structural, mechanical magnetic and growth of bacteria strains of the ball milled powders were studied as a function of milling time, t (t = 0h, 1h, 2h and 3h) by X-ray diffraction using the MAUD program which is based on the Rietveld method, vibrating sample magnetometer, and Fourier-transform infrared spectroscopy and ultraviolet–visible spectroscopy. The XRD results revealed the coexistence of the centered cubic α-Fe(P) solid solution and Co binary phase, for all milled samples. The average crystallite size of the formed solid solution and binary phase decreased with the milling time. The evolution of the mechanical properties "Young's Modulus and Poisson's Coefficient" demonstrated the stiffness and the deformation properties of the formed phase and solid solution. The milling process induced some important changes in the magnetic properties, whereas the variation of the saturation magnetization and coercivity was associated mainly with the particle size refinement, accumulation of microstrain and formation of solid solution α-Fe(P) and phase. Several fundamental magnetic parameters have been discussed as a function of milling time. The current study provides evidence that milled Fe powder mixtures with different concentrations have better antibacterial activity against Gram-positive strains and the same powder mixtures could be used as cofactor for the examined Gram-negative strains.

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