Magnetic and microwave properties of glass-coated amorphous ferromagnetic microwires

Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-coated microwires respectively. The vibrating sample magnetometer and vector network analyzer were used to study the magnetostatic and microwave properties of glass-coated microwires. The experimental results show that the effective anisotropy of an array of 150 microwires of 10 mm in length is large than that of one microwire of 10 mm in diameter and an array of 150 microwires of 1 mm in diameter. The natural ferromagnetic resonance takes place as the microwave magnetic component is perpendicular to the microwires axis, and the electric dipole resonance takes place as the microwire is long or the short microwire concentration is moderate. The natural ferromagnetic resonance shifts to higher frequency with the larger microwire concentration. The electric dipole resonance is governed by the microwires length and concentration. The glass-coated FeCuNbSiB microwires can be used to design EMI filters and microwave absorbing materials.

Photodetector based on Ruddlesden-Popper perovskite microwires with broader band detection

Recently,the two-dimensional(2D)form of Ruddlesden-Popper perovskite(RPP)has been widely studied.However,the synthesis of one-dimensional(1D)RPP is rarely reported.Here,we fabricated a photodetector based on RPP microwires(RPP-MWs)and compared it with a 2D-RPP photodetector.The results show that the RPP-MWs photodetector possesses a wider photoresponse range and higher responsivities of 233 A/W in the visible band and 30 A/W in the near-infrared(NIR)band.The analyses show that the synthesized RPP-MWs have a multi-layer,heterogeneous core-shell structure.This structure gives RPP-MWs a unique band structure,as well as abundant trap states and defect levels,which enable them to acquire better photoresponse performance.This configuration of RPP-MWs provides a new idea for the design and application of novel heterostructures.

Preparation and photodetection performance of high crystalline quality and large size β-Ga_(2)O_(3)microwires

Ultrawide band gap semiconductors are promising solar-blind ultraviolet(UV)photodetector materials due to their suitable bandgap,strong absorption and high sensitivity.Here,β-Ga_(2)O_(3)microwires with high crystal quality and large size were grown by the chemical vapor deposition(CVD)method.The microwires reach up to 1 cm in length and were single crystalline with low defect density.Owing to its high crystal quality,a metal–semiconductor–metal photodetector fabricated from a Ga_(2)O_(3)microwire showed a responsivity of 1.2 A/W at 240 nm with an ultrahigh UV/visible rejection ratio(R_(peak)/R_(400 nm))of 5.8×10^(5),indicating that the device has excellent spectral selectivity.In addition,no obvious persistent photoconductivity was observed in the test.The rise and decay time constants of the device were 0.13 and 0.14 s,respectively.This work not only provides a growth method for high-quality Ga_(2)O_(3)microwires,but also demonstrates the excellent performance of Ga_(2)O_(3)microwires in solar-blind ultraviolet detection.

A novel and facile wet-chemical method for synthesis of silver microwires

A novel and facile wet-chemical method for synthesis of silver microwires was developed.The well-defined particles were prepared by adding an iron（Ⅱ） sulfate heptahydrate solution into a silver nitrate solution containing citric acid drop by drop at 50 °C.The resulting products were characterized by scanning electron microscopy and X-ray diffraction.It was found that the particles consisted of numerous silver microwires.The reaction temperature greatly affected the morphologies of the as-prepared particles.Both of the mean length and width of the silver microwires increased with the decrease of the concentration of silver nitrate.And the lower concentration was unfavorable for the formation of more silver microwires.Similar findings were also observed when the concentration of iron（Ⅱ） sulfate was decreased.The amount of citric acid also greatly affected the shape of the as-prepared particles.It was concluded that citric acid was the key role in the formation of silver microwires via the Oswald ripening mechanism.

Magnetocaloric effect in Ni-Mn-In-Co microwires prepared by Taylor-Ulitovsky method

Ni-Mn-In-Co microwires with diameter of 30-100 μm are prepared by glass-coated metal filaments（Taylor–Ulitovsky） method. The effects of magnetic field on martensite transformation temperature in the as-prepared and annealed microwires are investigated using a physical property measurement system（PPMS）. Magnetocaloric effect（MCE） attributed to field-induced austenite transformation in the as-prepared and annealed microwires is analyzed indirectly from the isothermal magnetization（M-B） curves. The as-prepared microwire has a 7-layer modulated martensite structure（7M） at room temperature. The changes of austenite starting temperature induced by an external magnetic field（ΔAs/ΔB） in the as-prepared and annealed microwires are-1.6 and-4 K/T, respectively. Inverse martensite to austenite transformation exists in annealed microwires when an external magnetic field is applied at temperatures near As. The entropy change（ΔS） obtained in the annealed microwires is 3.0 J/（kg·K）, which is much larger than that in the as-prepared microwires 0.5 J/（kg·K）. The large entropy change and low price make Ni-Mn-In-Co microwires a potential working material in magnetic refrigeration.

Annealing effects on the microwave permittivity and permeability properties of Fe_(79)Si_(16)B_5 microwires and their microwave absorption performances

This paper reports that amorphous magnetic microwires （Fe79Si16Bs） have been fabricated by a melt-extraction technique and have been annealed at 600℃ and 750℃ respectively. Differential scanning calorimeter measurements show that nanocrystalline magnetic phase （α-Fe） has been formed in the amorphous matrix when it was annealed at 600℃. Hard magnetic phase （Fe2B） was formed in the microwires annealed at 750℃, which increases the magnetic coercivity. Microwave permittivity and permeability are found to be dependent on the microstruetures. The permittivity fitting results show that multi Lorentzian dispersion processes exist. For microwires annealed at 750℃, their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600℃. The microwave absorption performance of microwires annealed at 600℃ is found better than microwires annealed at 750℃.

Effect of annealing treatments on the microwave electromagnetic properties of amorphous FeCuNbSiB microwires

The amorphous FeCuNbSiB microwires are fabricated by using the melt extraction method and annealed separately at temperatures T = 573, 673, 723 and 773K for lh. The effect of annealing treatment on the microwaw electromagnetic properties of FeCuNbSiB wires/wax composites has been investigated for the first time. It is found that in a frequency range of 0.5-4.0 GHz, the complex permittivity, permeability, magnetic and electric loss tangents of FeCuNbSiB wires/wax composites are strongly dependent on the annealing temperature and frequency. For T = 573, 723 and 773K, two resonance peaks are found at frequency f = 1.2 and 3.3GHz. However, for T = 673K, only one resonance peak occurs at f = 3.3 GHz. The resonance peak at f = 1.2 GHz is believed to be due to the stress-induced anisotropy, while the resonance peak at f = 3.3 GHz is attributed to the random anisotropy.

Dielectrophoretic force distribution of growing microwires

The Dielectropheretic assembly of electrically functional microwires from nanopartical suspensions is introduced. Meanwhile growth mechanism of the microwires is discussed. The agglomeration is based on the polarization and mobility of particles caused by alternating electric fields, commonly referred to as dielectrophoresis (DEP). The spatial distributions of the electric potential, field and dieletrophoretic force are analytically calculated in terms of AC electrokinetics. The calculated results show that the electrophoretic force, very strong near the apex of the microwire, drops abruptly with increasing distance. The electrophoretic force near the apex of the microwire agrees well with the fact that the nanoparticles are highly concentrated at the end of the tip and subsequently aggregate to extend the wire in the direction of the field gradient.

Nanodots and microwires of ZrO_2 grown on LaAlO_3 by photo-assisted metal–organic chemical vapor deposition

ZrO_2 nanodots are successfully prepared on LaAlO_3（LAO）（100） substrates by photo-assisted metal-organic chemical vapor deposition（MOCVD）. It is indicated that the sizes and densities of ZrO_2 nanodots are controllable by modulating the growth temperature, oxygen partial pressure, and growth time. Meanwhile, the microwires are observed on the surfaces of substrates. It is found that there is an obvious competitive relationship between the nanodots and the microwires. In a growth temperature range from 500℃ to 660℃, the microwires turn longest and widest at 600℃, but in contrast, the nanodots grow into the smallest diameter at 600℃. This phenomenon could be illustrated by the energy barrier, decomposition rate of Zr（tmhd）_4, and mobility of atoms. In addition, growth time or oxygen partial pressure also affects the competitive relationship between the nanodots and the microwires. With increasing oxygen partial pressure from 451 Pa to 75_2 Pa,the microwires gradually grow larger while the nanodots become smaller. To further achieve the controllable growth, the coarsening effect of ZrO_2 is modified by varying the growth time, and the experimental results show that the coarsening effect of microwires is higher than that of nanodots by increasing the growth time to quickly minimize ZrO_2 energy density.

Micromagnetic Structure of Co-Rich Amorphous Microwires

Results on the magneto-optical investigation of near-surface micromagnetic structure (MMS) of Co69Fe4Si12B15 amorphous wires 10～50 μm in diameter are presented. The wires were prepared by the rapid solidification technique. The magnetic field H was applied along or perpendicular to the wire length. By scanning the light spot of 1 μm-diameter along the wire length, distributions of magnetization components (both parallel and perpendicular to the applied magnetic field) and also local hysteresis characteristics of the wires were measured. It was experimentally established that owing to the compressive stresses from quenching coupled with negative magnetostriction of Co-rich amorphous materials, the examined microwires have a circumferential magnetic anisotropy. In consequence, there are the near-surface alternate left- and right-handled circular domains in these samples. The dependencies of the circular domain width on the wire diameter and length were found. It was discovered that in the axial magnetic field local hysteresis loops are unhysteretic. It was proved that in this case the dominant mechanism of the wire magnetization reversal is rotation of local magnetization vectors in circular domains.

Effect of chemical ordering annealing on superelasticity of Ni-Mn-Ga-Fe ferromagnetic shape memory alloy microwires

Ni50Mn25Ga20Fe5 ferromagnetic shape memory alloy microwires with diameters of^30-50μm and grain sizes of^2-5μm were prepared by melt-extraction technique.A step-wise chemical ordering annealing was carried out to improve the superelasticity strain and recovery ratio which were hampered by the internal stress,compositional inhomogeneity,and high-density defects in the as-extracted Ni50Mn25Ga20Fe5 microwires.The annealed microwires exhibited enhanced atomic ordering degree,narrow thermal hysteresis,and high saturation magnetization under a low magnetic field.As a result,the annealed microwire showed decreased superelastic critical stress,improved reversibility,and a high superelastic strain(1.9%)with a large recovery ratio(>96%).This kind of filamentous material with superior superelastic effects may be promising materials for minor-devices.

Effects of Strain Rate and Texture on the Tensile Behavior of Pre-strained NiCr Microwires

The stress–strain behavior and strain rate sensitivity of pre-strained Ni80Cr20（Ni20Cr） were studied at strain rates from 4.8×10^（–4）s^（–1） to 1.1×10^（–1）s^（–1）. Specimens were prepared through cold drawing with abnormal plastic deformation. The texture of the specimen was characterized using electron backscatter diffraction. Results revealed that the ultimate tensile strength and ductility of the pre-strained Ni20Cr microwires simultaneously increased with increasing strain rate. Twinning-induced negative strain rate sensitivity was discovered. Positive strain rate sensitivity was present in fracture flow stress, whereas negative strain rate sensitivity was detected in flow stress values of σ_（0.5%） and σ_（1%）. Tensile test of the pre-strained Ni20Cr showed that twinning deformation predominated, whereas dislocation slip deformation dominated when twinning deformation reached saturation. The trends observed in the fractions of 2°-5°, 5°-15°, and 15°-180° grain boundaries confirmed that twinning deformation dominated the first stage.

Fe对Ni-Mn-Ga合金微丝形状记忆效应的影响

以Ni-Mn-Ga合金微丝为基础分析Fe元素掺杂前后对合金微丝的形状记忆效应的变化。用真空磁控钨极电弧熔炼炉制备Ni-Mn-Ga-Fe合金,并用高真空精密熔体抽拉设备将母合金制备成微丝。采用EDS能谱分析仪、DSC差示扫描量热分析仪、XRD、DMA动态机械分析仪,研究Fe元素掺杂Ni-Mn-Ga合金微丝后的物相、马氏体相变行为、微丝的形状记忆效应。结果表明,Ni-Mn-Ga-Fe合金微丝显示的是四方结构马氏体相和面心立方结构奥氏体相的混合相,对微丝采用步进式阶梯有序化热处理,有序化热处理能有效降低微丝内部缺陷,释放内应力,细化微丝内部晶粒,收缩晶格体积,马氏体孪晶界面更加平直,孪晶面更易移动,微丝的伸长率提高。在258 K下对制备态Ni-Mn-Ga-Fe合金微丝进行单程形状记忆的测试,拉伸到350 MPa后卸载到0 MPa,随后将微丝升温到奥氏体态后,应变恢复率为78.75%,而在289K对有序化热处理态Ni-Mn-Ga-Fe合金微丝进行单程形状记忆测试,应变恢复率达到100%。在126 MPa和240 MPa下分别对有序化热处理态三元Ni-Mn-Ga合金微丝和Ni-Mn-Ga-Fe合金微丝进行恒应力拉伸,两种微丝双程形状恢复能力均接近100%,但Ni-Mn-Ga-Fe合金微丝在发生形变时的弹性应变储能略高于Ni-Mn-Ga合金微丝。Fe的加入使得到的合金微丝的力学性能高于传统三元形状记忆合金微丝;制备态下和热处理态的Ni-Mn-Ga-Fe合金微丝的马氏体相变温度较Ni-Mn-Ga合金微丝分别提高6.0 K和11.5 K,热滞分别降低6.7 K和1.5 K。

Cu-4Ag合金微细丝拉拔极限预测模型

采用三室真空冷型竖引连铸设备制备了Cu-4Ag合金铸态杆坯,并利用连续冷拉拔变形得到了不同线径的Cu-4Ag合金微细丝,通过拉拔实验获取了不同线径下材料的屈服强度和抗拉强度;基于线径与强度的关系,构建了微细丝拉拔极限预测模型。结果表明,在拉拔过程中,Cu-4Ag合金微细丝的线径与抗拉强度密切相关,具有明显的尺寸效应;修正后的拉拔极限模型能够较为准确地预测不同线径的Cu-4Ag合金微细丝能够达到的拉拔极限。将拉拔极限模型产出的数据导入MATLAB中,构建了三维曲面模型,可以更为直观地分析材料的拉拔极限。

微导丝结合微导管辅助技术在瘤颈发出重要分支血管的颅内破裂动脉瘤栓塞中的应用

目的探讨微导丝结合微导管辅助分支血管保护技术在瘤颈发出重要分支血管的颅内破裂动脉瘤血管内治疗中的应用价值。方法回顾性分析2021年6月至2022年6月血管内栓塞治疗的8例瘤颈发出重要分支血管的颅内破裂动脉瘤的临床资料。术中使用微导丝携微导管放置于动脉瘤瘤颈处分支血管内,利用张力对分支血管予以保护,辅助行弹簧圈栓塞治疗。结果所有病例均顺利完成手术,术中未发生动脉瘤破裂或血管栓塞并发症。术后即刻造影显示,Raymond分级1级6例,2级2例;所有分支血管术后血流通畅。术后3~6个月随访,DSA显示动脉瘤均闭塞,无复发,分支血管通畅;GOS评分4~5分7例,3分1例。结论对于瘤颈发出重要分支血管的颅内破裂动脉瘤,术中利用微导丝结合微导管辅助分支血管保护技术行弹簧圈栓塞可行性好、安全性高、效果良好。

MICROWIRE总线与SPI总线的接口设计与应用

MICROWIRE总线与SPI总线是目前应用非常广泛的两种同步串行总线,由于两种总线协议的不完全兼容性,造成许多设备之间无法进行通信。通过对PIC16F73单片机的SPI串口时序和电机控制专用芯片SA866的MICROWIRE串口时序的研究,给出了正确配置SPI模式的方法,并通过软件的转换控制,成功解决了SPI与MICROWIRE两种不同协议之间相互通信的问题。

熔体纺丝纤维的磁热性能与磁制冷应用研究进展

本文对熔体纺丝合金纤维的磁热性能和磁制冷应用的研究进展进行了综述,总结了不同种类具有磁热性能的合金纤维在磁场驱动下能够产生的磁熵变最大值、半高宽和磁制冷能力。概述了熔体纺丝法的基本原理和操作过程,以及小尺寸纤维形态在实际磁制冷机中的应用优势,并重点介绍了将合金制备成纤维形态能够解决大块合金中存在的相关问题,描述了不同种合金纤维产生磁热效应的原理,阐明了纤维相变特征对制冷温度区间、磁熵变及磁热效应的影响机制,最后总结了合金纤维在活性蓄热器中的制冷功率和性能系数的研究情况,简述了将小尺寸合金纤维大批量应用于实际磁制冷装置以解决该类装置制冷效率低、制冷功率小的可行性。

电路微导线激光驱动微滴喷射沉积打印

激光驱动微滴打印是一种高分辨率、高柔性和材料适应性广的金属微增材制造工艺,能实现纯金属微结构打印。面向电路微导线打印,目前的激光驱动微滴沉积工艺规律认识还不清晰。因此基于纳秒光纤激光驱动微滴打印系统,实现了直径5μm的铜微滴阵列的沉积,沉积位置偏差为±5μm。研究不同工艺参数下的激光驱动微滴沉积微导线形貌,发现由于存在微滴沉积位置偏差,交替沉积策略比微滴顺序沉积更适合打印微导线;当沉积微滴搭接间距减至1.5μm时,可形成联通的导线打印;微滴转移间距从50μm增至200μm,打印微导线的线宽增加约2倍;实现线宽为15μm的微导线打印,并通过四探针法测试获得的微导线电阻率为实体材料的9倍。

Microstructure and magnetocaloric properties of melt-extracted SmGdDyCoAl high-entropy amorphous microwires

This paper presents a systematic investigation of the microstructure and magnetocaloric properties of melt-extracted Sm_(20)Gd_(20)Dy_(20)Co_(20)Al_(20)high-entropy microwires.The fabricated wires exhibited an amorphous structure,and the temperature interval of the undercooled liquid AT was 45 K.The microwires underwent a second-order magnetic transition from a ferromagnetic to a paramagnetic state near the Curie temperature(T_(C)=52 K),The maximum magnetic entropy change(-ΔS_M^(max)),the relative cooling power and the refrigeration capacity reached 6.34 J·kg^(-1)·K^(-1).422.09 J·kg^(-1)and 332.94 J·kg^(-1),respectively,under a magnetic field change of 5 T.In addition,the temperature-averaged entropy changes with two temperature lifts(3 and 10 K)were 6.32 and 6.27 J·kg^(-1)·K^(-1),respectively.The good magnetocalorie performance highlights the significant potential for the Sm_(20)Gd_(20)Dy_(20)Co_(20)Al_(20)microwires to be used as magnetic refrigerant materials in low-temperature region applications.This work will serve as a valuable reference for future investigations on low-temperature high-entropy magnetocaloric materials.

皮秒激光驱动微丝靶产生的超热电子能谱实验研究

目的 针对激光辐照平面靶中超热电子束流发散角过大以及产生的X光源亮度不足的问题,提出采用高功率皮秒激光辐照微丝靶,研究电子再循环效应对超热电子束流和X光源特性的影响。方法 实验在“星光-Ⅲ”装置皮秒束激光器上进行,分别采用直径10μm的钼和金丝靶作为X射线背光源。利用针孔相机在激光反射方向测量X光焦斑,靶前法线方向布置电子磁谱仪测量逃逸出靶的超热电子能谱。结果 获得的X光焦斑的纵向尺寸最小值达到10μm,与丝靶直径相当。超热电子能谱结果显示自持独立钼丝和金丝中最高温度分别为863 keV和816keV,比对应的带CH衬底丝靶中的超热电子温度和数目均有显著提升。结论 说明移除支撑丝靶的低密度衬底是增强电子再循环效应的有效途径,通过这种方式能够提高超热电子束流的强度和集中度,增强轫致辐射强度,从而获得微焦点和高亮度的X射线源。