Qikui Man

Effects of B and Si contents on glass-forming ability and soft-magnetic properties in (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x glassy alloys

The effects of B and Si contents on the glass-forming ability (GFA) and soft-magnetic properties of (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x (x=22–30) alloys were investigated. The thermal stability of the supercooled liquid increased with increasing the B and Si contents from x=24 to 28, and accompanying the decreases of liquidus temperature of alloys. As a result, The (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x bulk glassy alloys with diameters up to 3.5 mm were synthesized in the composition range of x=24–28. In addition to high GFA, the Co-based glassy alloys exhibit excellent soft-magnetic properties as well, i.e., moderate saturation magnetization of 0.51–0.72 T, low coercive force of 0.4–1.5 A/m, and high initial permeability of 22 340–29 570 at 1 kHz under a field of 1 A/m.

Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

The effects of heavy rare earth (RE) additions on the Curie temperature (T-C) and magnetocaloric effect of the Fe-RE-B-Nb (RE-Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T-C in a large temperature range of 120K without significantly decreasing the magnetic entropy change (Delta S-M) and refrigerant capacity (RC) of the alloys. The observed values of Delta S-M and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd5Ge1.9Si2Fe0.1. The tunable T-C and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

Correlation of atomic packing with the boson peak in amorphous alloys

Boson peaks (BP) have been observed from phonon specific heats in 10 studied amorphous alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied amorphous alloys and 56 reported amorphous alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in amorphous alloys, and (b) the atomic packing in amorphous alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied amorphous alloys. This finding provides a new perspective for atomic packing in amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.

Giant magnetoimpedance effect enhanced by thermoplastic drawing

We performed thermoplastic forming (TPF) on FeCoNbB metallic glass ribbons with a supercooled liquid region exceeding 100 K, and found the sample after TPF is still completely amorphous. More importantly, the giant magnetoimpedance (GMI) effect was improved after the forming process: the maximum GMI ratio and sensitivity increased from 41% to 12.3%/Oe in the case of as-cast sample to 280% and 358.2%/Oe in the case of resulting sample after TPF, respectively. The hysteresis loops and domain patterns were subsequently studied, which revealed that the primary factor leading to the improvement of the GMI effect was the enhanced longitudinal magnetic anisotropy induced by the TPF process. We therefore assume that TPF is an effective way that improves the GMI effect, which differs from conventional annealing methods.

The soft magnetic properties of ring-shaped (Co0.6Fe0.3Ni0.1)68(B0.811Si0.189)27Nb5 bulk metallic glasses

Ring-shaped (Co0.6Fe0.3Ni0.1)68(B0.811Si0.189)27Nb5 bulk samples with an outer diameter of 10 mm, an inner diameter of 6 mm, and a thickness of 1 mm were successfully prepared by copper mold casting. The effects of annealing treatments on magnetic properties of the ring-shaped bulk sample were investigated. After the optimum annealing treatment, the resulting ring-shaped bulk sample exhibits good magnetic properties, i.e., low coercive force of 0.55 A/m, high maximum permeability of 433 000, and high permeability of 19 400 at 50 Hz under an AC field amplitude of 1.2 A/m, respectively. In addition, the ring-shaped bulk sample also shows low core loss of 0.09 W/kg at 50 Hz under induction of 0.5 T. The synthesis of ring-shaped bulk samples with good magnetic properties is encouraging for their potential applications as functional materials in the future.

A skin-inspired tactile sensor for smart prosthetics

A skin-inspired tactile sensor achieved transduction of digital-frequency signals by an inductance-capacitance oscillation mechanism. Recent achievements in the field of electronic skin have provided promising technology for prosthetic systems. However, the development of a bionic tactile-perception system that exhibits integrated stimuli sensing and neuron-like information-processing functionalities in a low-pressure regime remains a challenge. Here, we demonstrate a tactile sensor for smart prosthetics based on giant magneto-impedance (GMI) material embedded with an air gap. The sensor exhibits a high sensitivity of 120 newton−1 (or 4.4 kilopascal−1) and a very low detection limit of 10 micronewtons (or 0.3 pascals). The integration of the tactile sensor with an inductance-capacitance (LC) oscillation circuit enabled direct transduction of force stimuli into digital-frequency signals. The frequency increased with the force stimuli, consistent with the relationship between stimuli and human responses. The minimum loading of 50 micronewtons (or 1.25 pascals), which is less than the sensing threshold value of human skin, was also encoded into the frequency, similar to the pulse waveform of humans. The proposed tactile sensor not only showed desirable sensitivity and low detection limit but also exhibited transduction of digital-frequency signals like human stimuli responses. These features of the GMI-based tactile sensor show potential for its applications in smart prosthetics, especially prosthetic limbs that can functionally replace natural limbs.