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The (Fe40Ni40SixByCu1)0.97Nb0.03 (Si/B = 3:1, 2:1, 1:1, 1:2 and 1:3) alloys were fabricated through the melt-spun technique. The effects of Si/B ratio on the glass-forming ability (GFA), phase transitions and soft magnetic properties were investigated. Results showed that when Si/B = 1:1, 1:2 and 1:3, the GFA of the FeNiSiBCuNb alloy is good, and the amorphous structure is homogeneous. We found a phase transition from the amorphous phase to α-Fe (Si) phase and then to γ-(Fe,Ni)Si phase in Si/B = 1:1 alloy by employing a simple heat treatment process. The alloys with Si/B = 1:1 and 1:2 containing a low coercivity of 0.30 A/m and 0.25 A/m domain structures were characterized with magneto-optical Kerr microscope (MOKE) to unveil that the internal stress relief is beneficial to the magnetization process. The three alloys exhibit different crystallization behaviors, and moderate Si can effectively inhibit γ-(FeNi) grains overgrowth.

(Fe40Ni40B19Cu1)97Nb3 magnetic amorphous alloys have been prepared by a melt-spun method, and their crystallization behavior and kinetics have been investigated. The results showed that under non-i...

Fe81−xGaxB15Nb3Cu1 (x = 0, 3, 6, 9, 12 at%) ribbons were fabricated by using melt-spun method and their crystallization kinetics, magnetic properties and microstructure were investigated. We found that the small quenched-in Fe–Ga clusters were formed in the as-spun ribbons with Ga addition. Besides, proper Ga addition could suppress the precipitation of Fe2B phase. During annealing, addition of Ga could provide Fe–Ga clusters to be nucleation sites for the α-Fe(Ga) phase, and could inhibit the initial grain growth. With the increase of annealing temperature above 475 °C, the crystallization was controlled by both Fe–Ga and Cu clusters, which effectively refined the grain size by facilitating the nucleation and increased the crystallization volume fraction. Consequently, in the ribbon with 6 at% Ga, the grains turned out to be the minimum in the mean size of 8 nm, and the optimal soft magnetic properties with coercivity at 6.8 A/m and saturation magnetization at 167 emu/g were obtained at annealing temperature of 490 °C for 3 min.

In this paper, Fe76Ga5Ge5B13Cu1 ribbon was prepared by melt spinning method and its thermal stability and non-isothermal crystallization kinetics were analyzed. It is found that the primary crystallization phase is α-Fe(Ga,Ge), following by the precipitation of Fe-B compounds. Besides, Kissinger and Ozawa methods were utilized to calculate the initial activation energy Ex and apparent activation energy Ea. The results show that Ex1 > Ea1, which is due to that the diffusion of Ga and Ge is difficult during the nucleation process but left a channel for the subsequent diffusion of atoms. In addition, Avrami index n was calculated by Johnson-Mehl-Avrami-Kolmogorov (JMAK) model and the crystallization mechanism of Fe76Ga5Ge5B13Cu1 alloy was analyzed. For the alloy with grains or clusters embedded in the amorphous matrix, it is concluded that the annealing condition with a higher heating rate is more conducive to obtain homogeneous nanocrystalline and improve soft magnetic properties.

The Fe79-xB20NbxCu1 (x = 0, 2, 4, 6, 8) fibers were fabricated using the melt-spinning method and the microstructure and magnetic property of the fibers after annealing were investigated. The results showed that coercivity of the as-spun fibers increased slightly with the growth of Nb/Fe atomic ratio. Fe23B6-type phase precipitated from amorphous matrix after annealed at 550 °C and then transformed into α-Fe, Fe2B and FeNbB phases with the increase of annealing temperature which corresponded to specific crystallization processes. The Fe23B6-type phase with a lattice parameter of 1.0735 nm was obtained by selected-area electron diffraction pattern and high-resolution transmission electron microscope images. Moreover, after annealed at 530 °C for 3 min, the minimum Hc at 7 A/m of Fe77B20Nb2Cu1 fibers was found.

The effect of annealing on the microstructure and magnetic softness of Fe77.5Si7.5Ga6B9 ribbons has been investigated, and the contribution of Ga addition to the saturation magnetization has been discussed. It was found that as-spun ribbon shown two steps of crystallization processes, which corresponded to the precipitation of α-Fe (Ga, Si) and Fe2B. Critical phase separation was detected in the ribbons that prepared at the wheel speed of 25 m/s, which could be due to the heterogenous distribution of Fe and Ga atoms according to X-ray photoelectron spectroscopy results. In addition, Ga in the nearest neighbour position of Fe could improve the magnetic moment μFe, but the participation of Si could diminish the improvement, owing to the free electrons transference between Fe, Ga and Si, and the phase dependence of exchange interacting strength of Fe atoms. Besides, The first principle has a great potential to study the saturation magnetization evolution of Fe-based nanocrystalline alloys.

We established the vibration governing equation for a magnetoelastic (ME) biosensor with target loading in liquid. Based on the equation, a numerical simulation approach was used to determine the effect of the target loading position and viscous damping coefficient on the node (&ldquo, blind points&rdquo, ) and mass sensitivity (Sm) of an ME biosensor under different order resonances. The results indicate that viscous damping force causes the specific nodes shift but does not affect the overall variation trend of Sm as the change of target loading position and the effect on Sm gradually reduces when the target approaches to the node. In addition, Sm decreases with the increase of viscous damping coefficient but the tendency becomes weak at high-order resonance. Moreover, the effect of target loading position on Sm decreases with the increase of viscous damping coefficient. Finally, the results provide certain guidance on improving the mass sensitivity of an ME biosensor in liquid by controlling the target loading position.

In the present work, (Fe40Ni40SixByCu1)0.97Nb0.03 (Si/B = 1:1, 1:2, and 1:3) alloys were prepared by the as-melt spun method. The effect of different Si/B ratios on the isothermal crystallization behavior of FeNiSiBCuNb glass alloys were investigated. The activation energies of the Si/B = 1:1, 1:2, and 1:3 alloys for nucleation and grain growth were calculated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model as 123.6 kJ/mol and 207.3 kJ/mol, 151.0 kJ/mol and 251.3 kJ/mol, and 88.6 kJ/mol and 170.0 kJ/mol respectively; hence, crystal nuclei needed to cross a higher energy barrier in the growth process. The variation of local Avrami exponent n(α) with crystallization fraction α demonstrates that the crystallization mechanism was divided into three stages: i: initial crystallization stage with n＞2, indicating that α-Fe(Si) phase or γ-(Fe, Ni)Si phase with a high nucleation rate stage, ii: middle crystallization stage with n≈2, indicating that FeNiB phase with a stable nucleation stage, and iii: the end of crystallization stage with n＜2, indicating that γ-(Fe, Ni)Si and FeNiB phases with a growth stage; The crystallization process was transformed from diffusion-controlled one-dimensional growth to diffusion-controlled three-dimensional growth.

Arrays of amorphous CoFeB nanowires with the diameter of 250 nm and length of 20 μm were fabricated by electrodepositing in pores of anodic aluminum oxide (AAO) templates. The corresponding changes of coercivity (Hc), remanence squareness (Mr/Ms), and the shape of hysteresis loops of NWs before and after annealing with the microstructure evolution have been investigated. The XRD and TEM results showed the precipitation of partial Co nanocrystallites and complete crystallization for the annealing treatment at 573 K and 773 K, respectively. The VSM results indicated a strong magnetic anisotropy in the amorphous nanowires and the easy magnetization axis was in perpendicular to the long wire axis. Both Hc and Mr/Ms increased with increasing annealing temperature. The magnetization reversal process occurred by the curling model for the amorphous nanowires and exhibited a transition for magnetization reversal after thermal annealing. In all, the magnetic properties of CoFeB nanowires can be controlled by tuning their microstructure with thermal annealing.

The effect of partial substitution of Si by Ga on the microstructure and soft magnetic properties of FINEMET-like Fe73.5Si13.5−xNb3B9Cu1Gax (x = 0, 3, 6, 9, 12 at.%) alloys has been investigated. It was found that the primary crystallization of ribbons was gradually changed from α-Fe (Si) into α-Fe (Ga, Si) phase with the increase of Ga content. Besides, the Fe-Ga clusters were detected in the amorphous ribbon with x = 6, which could provide nucleation sites for the α-Fe (Ga, Si) phase. In such case, the crystallization temperature of the ribbons with Ga addition was lower than that of ribbon without Ga addition. For the ribbon with x = 6, the precipitation of Ga element was priority to that of Si, which leads to the ‘increase-decrease’ tendency for the changes of lattice parameter with the increase of annealing temperature. Meanwhile, compared to the α-Fe (Si) phase with enrichment of Si for x = 0 ribbon, the α-Fe (Ga, Si) phase with high Ga and low Si concentration for the x = 6 ribbon was obtained, together with fine grain size (11 nm) of α-Fe (Ga, Si) phase, resulting to the same low coercivity (0.24 A/m), higher saturation magnetization (1.37 T) and maximum permeability after annealed at 455 °C for 1 min.

Amorphous (Fe40Ni40B19Cu1)100−x Nb x (x = 1, 3, 5, 7) ribbons are prepared by using the melt-spinning method. We find that the glass forming ability (GFA) of the as-melt spun ribbons is significantly improved by adding Nb element. In addition, the thermal stability evaluated in steps of Δ T = T x 2 − T x 1 effectively increases from 16 K to 75 K with Nb content increasing. The as-melt spun (Fe40Ni40B19Cu1)97Nb3 ribbon exhibits a lowest coercivity of 2 A/m and relatively large saturation magnetization of 103.7 A · m 2 / kg and thus it can be further treated by being annealed at 809 K. The crystallization behavior is confirmed to be determined by two individual crystallization processes corresponding to the precipitation of (Fe,Ni)23B6 phase and γ-(Fe,Ni) phase. With increasing annealing time, the single (Fe,Ni)23B6 phase can be transformed into a mixture of (Fe,Ni)23B6 and γ-(Fe,Ni) phase, and the grain size of γ-(Fe, Ni) phase increases from 5 nm to 80 nm while the grain size of (Fe,Ni)23B6 remains almost unchanged. Finally, we find that the grain growth in each of (Fe,Ni)23B6 and γ-(Fe, Ni) deteriorates the overall magnetic properties.

Background Fe80B20 amorphous alloys exhibit excellent soft magnetic properties, high abrasive resistance and outstanding corrosion resistance. In this work, Fe80B20 amorphous micro-fibers with HC of 3.33 Oe were firstly fabricated and the effects of annealing temperature on the structure and magnetic properties of the fibers were investigated. Methods In this study, Fe80B20 amorphous fibers were prepared by the single roller melt-spinning method. The structures of as-spun and annealed fibers were investigated by X-ray diffractometer (XRD) (PANalytical X,Pert Power) using Cu Kα radiation. The morphology of the fibers was observed by scanning electron microscopy (SEM) (HITACHI-S4800). Differential scanning calorimetry (DSC) measurements of the fibers were performed on Mettler Toledo TGA/DSC1 device under N2 protection. Vibrating sample magnetometer (VSM, Versalab) was used to examine the magnetic properties of the fibers. The resonance behavior of the fibers was characterized by an impedance analyzer (Agilent 4294A) with a home-made copper coil. Results The X-ray diffusion (XRD) patterns show that the fibers remain amorphous structure until the annealing temperature reaches 500°C. The differential scanning calorimetry (DSC) results show that the crystallization temperature of the fibers is 449°C. The crystallization activation energy is calculated to be 221 kJ/mol using Kissinger formula. The scanning electron microscopy (SEM) images show that a few dendrites appear at the fiber surface after annealing. The result indicates that the coercivity HC (//) and HC (⊥) slightly increases with increasing annealing temperature until 400°C, and then dramatically increases with further increasing annealing temperature which is due to significant increase in magneto-crystalline anisotropy and magneto-elastic anisotropy. The Q value firstly increases slightly when the annealing temperature rises from room temperature (RT) to 300°C, then decreases until 400°C. Eventually, the value of Q increases to ∼2000 at annealing temperature of 500°C. Conclusions In this study, Fe80B20 amorphous fibers with the diameter of 60 μm were prepared by the single roller melt-spinning method and annealed at 200°C, 300°C, 400°C, and 500°C, respectively. XRD results indicate that the fiber structure remains amorphous when the annealing temperature is below 400°C. α-Fe phase and Fe3B phase appear when the annealing temperature rises to 500°C, which is above the crystallization temperature of 449°C. The recrystallization activation energy is calculated to be 221 kJ/mol. The coercivity increases with increasing annealing temperature, which attributes to the increase of total anisotropy. All the as-spun and annealed fibers exhibit good resonance behavior for magnetostrictive sensors.

In this work, we propose a novel wireless actuator which is composed of magnetostrictive material/copper bi-layer film. The actuator can be controlled to move like a snake bi-directionally along a pipe by tuning the frequency of external magnetic field near its first order resonant frequency. The governing equation for the actuator is established and the vibration mode shape function is derived. Theoretical analysis shows that motion of the actuator is achieved by asymmetric vibration mode shape, specific vibration bending deformation, and effective net total impacting force. The simulation and experimental results well confirm the theoretical analysis. This work provides contribution to the development of wireless micro robots and autonomous magnetostrictive sensors.