Amorphous-crystalline Ni-Fe powder mixture: Hydrogenation and annealing effects on microstructure and electrical and magnetic properties

Abstract

The hydrogenation of a crystalline Ni-Fe (80 wt.% Ni, 20 wt.% Fe) powder mixture leads to the formation of a mixture of Face Centered Cubic (FCC)-Ni and FCC-Fe phase nanocrystals embedded in an amorphous matrix. The magnetic susceptibility of the nanostructured powder is 2.1 times higher than that of the as-produced crystalline mixture. Heating in the temperature range 420-590 K causes structural relaxation in the hydrogenated powder, resulting in an increase of the magnetic susceptibility and a decrease of the electrical resistivity. During the heating procedure, the reorientation of magnetic domains in nickel and iron takes place in the temperature range 580-650 K and 790-850 K, respectively. In the pressed sample from the powder mixture, the crystallization of the amorphous phase of nickel and its FCC lattice crystalline grain growth occurs in the temperature range 620-873 K causing a decrease in the magnetic susceptibility of the nickel FCC phase and a sudden drop in the electrical resistivity. Prolonged heating of the mixed powders at 873K results in the formation of a Ni-Fe solid solution with higher magnetic susceptibility than the starting mixture.

Microstructure, wear and corrosion properties of NiB-TiC composite materials produced by powder metallurgy method

“…This method has been replaced by powder metallurgy because the high strength alloys used in the construction of gas turbine discs are difficult to be forged. Further advantages of this method are the ease of dust particle size control and minimization of errors such as gas gap [12]. Mechanical alloying of powder metallurgy methods, production of nano-sized powders and melting temperature are the methods that are applied as an economical and versatile production technique for obtaining various metallic alloys.…”

The influence of barium ferrite nanoparticles on morphological and mechanical properties of ethyl cellulose based nanocomposites

“…Earlier types of membranes were dominantly composed of ceramic and metallic materials. The named classes of materials offer excellent mechanical and thermal properties, but also involve high operating costs [6,7]. Advances in polymer science and engineering have opened possibilities for their use in the membrane technology for gas separation, offering simple processing, low cost materials, with potentially high-purity oxygen product.…”

Effect of the degree of plastic deformation on the thermal electromotive force of cu-x5crni1810 steel thermocouple

“…At room temperature, the metastable state of most deformed metals as well as of steel does not transform into a stable state at an appreciable rate since thermal energy is not large enough to overcome the activation energy for microstructural ordering [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. At higher temperatures, thermal energy reaches the value of the activation energy.…”

“…As temperature increases, structural relaxation occurs in metals and alloys at temperatures lower than crystallization temperatures. This results in short-range ordering, which causes changes in physical and chemical properties as well as in the TEMF [16][17][18][19][20][21][22][23][24][25][26][27]. When temperature is above the crystallization temperature, nanocrystals first appear in the amorphous matrix.…”

“…These nanocrystals grow into larger crystals during crystallization. The appearance and growth of crystals induce microstructural changes that affect the mechanical, magnetic and chemical properties as well as the TEMF of the material [16][17][18][19][20][21][22][23][24][25][26][27]. H. Chiriac et al [32][33][34] observed a correlation between the TEMF and the evolution of the crystallization process from an amorphous state over a nanocrystalline to a crystalline state of Fe 90 Cu 1 Nb 3 Si 13.5 BB 9 , Fe 90 Hf 7 B 3 B , Fe 90 Zr 7 BB 3 and Fe 77.5 Si 7.5 B 15 B alloys.…”