• Proceedings of the Korean Magnestics Society Conference
• /
• 2005.06a
• /
• pp.142-143
• /
• 2005

• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.12a
• /
• pp.161.1-161.1
• /
• 2008

• Journal of Magnetics
• /
• v.11 no.1
• /
• pp.36-42
• /
• 2006

In this report, we demonstrate a comprehensive analysis of the effects of Au addition on the microstructure and magnetic properties of $Fe_{73.5}Si_{13.5}B_{9}Nb_{3}Au_1$ Finemet-type alloy. It was found that the as-quenched alloys were the amorphous state and turned into nanocrystalline state under heat treatments. The DSC analysis indicates that the sharply exothermal peak corresponding to the crystallization of the $\alpha-Fe(Si)$ was observed at $547-579^{\circ}C$ depending on the heating rates, which is little higher than that of original Finemet (542-$570{^{\circ}C}$, respectively). Besides, the thermomagnetic result confirmed that the full substitution of Cu by Au with the single phase structure in the M(T) curve along cooling cycle. Ultrasoft magnetic properties of the nanocrystallized samples were significantly enhanced by the proper annealing such as the increase of permeability and the decrease of the coercivity. The optimum annealing condition was found at the annealing temperature of $540^{\circ}C$ and the increase of the annealing time up to 90 min.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2000.09a
• /
• pp.473-479
• /
• 2000

The nanocrystalline Fe$_{84}$Zr$_{7}$B$_{6}$Cu$_{1}$ $Al_{2}$ alloy was annealed at 450 $^{\circ}C$ and 550 $^{\circ}C$ for l hour to achieve the ultra-soft magnetic properties such as large magnetoimpedence ratio(MIR), the incremental permeability ratio(PR), nearly zero coercivity, zero magnetostriction, etc. The PR and MIR of the sample were measured from 100 kHz to 10 MHz at a cryogenic chamber where the temperature can be varie from 10 K to 300 K. The increment of MIR value is proportional to increasing temperature. The maximum PR values measured at high frequency above 1 MHz remain almost same despite of the temperature variation from 10 K to 300 K except the sharpness in PR curves. However, the maximum PR values measured below 1 MHz show drastic increment at above 150K due to thermal activation of magnetic domains.s.s.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.880-894
• /
• 1995

Magnetic properties of $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}(x=\;3,\;4,\;5)$ rrelt-spun alloys with 6 at% B content were studied aiming for finding out a new $\alpha$-Fe based Nd-Fe-B nanocrystalline alloy with good hard magnetic properties. $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}$ melt-spun alloys prepared by RSP crystallized to nanocrystalline phase. An optimally annealed $Nd_{3}{(Fe_{0.9}Co_{0.1})}_{87}B_{6}Nb_{3}Cu_{1}$ melt-spun alloys had larger volume ratio of $\alpha$-Fe(Co) than that of higher Nd content alloy and showed high remanence of about 1.6 T. On the contrary, the increase of Nd content in $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}$ alloys gave rise to gradual increase of an amount of $Nd_{2}{(Fe,\;Co)}_{14}B$ phase and improved coercivity. An optimally annealed $Nd_{5}{(Fe_{0.9}Co_{0.1})}_{85}B_{6}Nb_{3}Cu_{1}$ alloy showed the most improved hard mag¬netic properties. The remanence, coercivityand energy product of the alloy were 1.35 T, 219 kA/m (2.75 kOe), and $129\;kJ/m^{3}$ (16.2 MGOe), respectively.

• Journal of the Korean institute of surface engineering
• /
• v.38 no.4
• /
• pp.156-162
• /
• 2005

Nickel-iron nanocrystalline alloys with different compositions and grain sizes were fabricated by electro-plating for MEMS devices. The iron content of the deposits was changed by varying the nickel/iron ion ratio in the electrolyte. X-ray diffraction (XRD) analysis was applied for measuring the strength of the texture and grain size of the deposits. The nickel/iron atom ratio of the deposits was analyzed by EDS. The hardness of the alloys was evaluated by Vickers hardness indenter. The internal stress of the deposits was measured by Thin Film Stress Measurement using Stoney's formula. Surface morphology and roughness were investigated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results of this study revealed that at a grain size of approximately $17\~24$nm the hardness, internal stress and roughness depend strongly on the iron content. With increasing the iron content, the hardness and internal stress of the deposits increased. An excellent correlation between the increase in the internal stress and the loss of (200) texture was found.

• Korean Journal of Metals and Materials
• /
• v.46 no.7
• /
• pp.420-426
• /
• 2008

By using electrodeposition, we developed a new method to produce Ni/Invar bimetal sheets, which have been used for the present study to investigate the texture evolution during annealing. The grains of electrodeposited Ni were columnar, while those of electrodeposited Fe-Ni alloy were nanocrystalline. These different parts of the bimetal underwent different evolution of textures and microstructures during annealing. In the nanocrystalline Invar, the as-deposited textures were of fiber-type characterized by strong <100>//ND and weak <111>//ND components, and the occurrence of grain growth resulted in the strong development of the <111>//ND fiber texture with the minor <100> // ND components. On the other hand, in the columnar-structured Ni part, the as-deposited <110>//ND fiber texture transformed to the <112>//ND fiber texture due to recrystallization occurring above $550^{\circ}C$. The development of microtextures which took place during annealing in the Ni/Invar interfacial regions was investigated by using the OIM analysis, and discussed in terms of the effect of atomic diffusion across the interfaces.

• Journal of Magnetics
• /
• v.7 no.1
• /
• pp.21-23
• /
• 2002

The magnetoimpedance of $Fe_{91.5-x}Zr_7B_xCu_1Al_{0.5}$alloys has been measured to investigate the influence of structural changes in the nanocrystallization process after thermal treatment. Annealing was performed at temperatures of $350^\circ{C}$, $450^\circ{C}$, and $550^\circ{C}$ for 1 hour in a vacuum. Ultra soft magnetic behavior was observed in the samples annealed at $550^\circ{C}$. The magnetoimpedance ratio and the longitudinal permeability ratio coincided with the softness of the magnetic properties of the thermally treated samples.

• Journal of Powder Materials
• /
• v.13 no.5 s.58
• /
• pp.336-339
• /
• 2006

Magnetic properties of nanostructured materials are affected in complicated manner by their microstructure such as pain size (or particle size), internal strain and crystal structure. Thus, studies on the synthesis of nanostructured materials with controlled microstructure are necessary fur a significant improvement in magnetic properties. In the present work, nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated from the powder mixtures of (99.9% purity) $FeCl_2$ and $CoCl_2$ by chemical solution mixing and hydrogen reduction.

• Journal of Powder Materials
• /
• v.10 no.3
• /
• pp.164-167
• /
• 2003

The mechanical alloying effect has been studied on the three Cu-based alloy systems with a positive heat of mixing. The extended bcc solid solution has been formed in the Cu-V system and an amorphous phase in the Cu-Ta system. However, it is round that a mixture of nanocrystalline Cu and Mo Is formed in the Cu-Mo system. The neutron diffraction has been employed at a main tool to characterize the detailed amorphization process. The formation of an amorphous phase in Cu-Ta system can be understood by assuming that the smaller Cu atoms preferentially enter into the bcc Ta lattice during ball milling.