Multi-phase nanocrystallization induced fast degradation of methyl orange by annealing Fe-based amorphous ribbons

Different from the common understanding that crystallization deteriorates the degradation capability of amorphous alloys, we show here that the Fe-based multi-phase nanocrystalline ribbons (Fe-MNRs) exhibit 3 and 17 times higher degradation rate than its amorphous counterpart and the conventional zero valent iron powders, respectively. The formation of multi-phase nanocrystals and nanoporous structure resulted from selective corrosion during degradation is responsible for the high degradation capability of Fe-MNRs. The present results suggest that suitable nano-crystallization annealing treatment could be a novel approach to enhance the degradation capability of Fe-based amorphous alloys.     

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.     

Microstructure and properties of cold consolidated amorphous ribbons from (NiCu)ZrTiAlSi alloys

Amorphous ribbons of compositions (Ni₅₆Cu₂)Zr₁₈Ti₁₃Al₆Si₅ and (Ni₃₆Cu₂₃)Zr₁₈Ti₁₄Al₅Si₄ were consolidated by high pressure torsion (HPT) at room temperature. In the HPT experiments a 6 GPa pressure and two turns were applied. Samples in the form of discs, 6–7 times thicker than the ribbons and about 10 mm in diameter were achieved. The minimal deformation for the homogenous consolidation was estimated to be in the range of 400%. XRD showed that the microstructure was dependent on the composition. The sample with high Cu content remained amorphous while the sample with low Cu content revealed some crystallization. DSC experiments allowed a comparison of the glass transition temperature T_g and crystallization process of the amorphous ribbon and HPT sample which were different. The glass transition temperature T_g of the amorphous HPT sample of (Ni₃₆Cu₂₃)Zr₁₈Ti₁₄Al₅Si₄ composition decreased. For both alloys the nanohardness and the elastic modules showed decrease for cold consolidated samples in comparison to the ribbons.     

退火工艺对Co71．8Fe4．9Nb0．8Si7．5815非晶薄带巨磁阻抗效应的影响

采用四端法研究了退火处理T艺对Co71.8Fe4.9Nb0.8Si7.5B15非晶薄带巨磁阻抗效应的影响.结果表明,Co71.8Fe4.9Nb0.8Si7.5B15非晶薄带试样经350 ℃保温60 min退火处理后,样品的内应力得到有效释放,大大改善了样品的软磁特性,得到了最大的巨磁阻抗效应(GMI).在8 MHz的交变电流频率下,得到了24%的最大磁阻抗比.XRD分析表明,样品发生晶化后将降低巨磁阻抗(GMI)效应.     

Mechanical properties and thermal neutron shielding efficiency of high B amorphous ribbons in the Fe-B-Mo-Cr system

For thermal neutron shielding applications, high boron amorphous ribbons with the compositions of Fe_72-xB₂₅-Mo₃Cr_x (where x = 0, 5, 10, 15 or 20 at%) have been developed. From the morphological and compositional analysis of vein patterns formed on the fracture surfaces of the ribbons, the segregation of boron within shear band regions was identified and discussed with reference to “free volume concentration” and “temperature rise” models that had been proposed independently. High boron amorphous ribbons with optimum amounts of Cr exhibit excellent thermal neutron shielding efficiency in combination with mechanical properties such as tensile strength and bending flexibility. Moreover, corrosion resistance of the amorphous ribbons can be effectively enhanced through proper Cr additions, thereby expanding their structural applications in the nuclear industry.     

退火对非晶合金磁特性及铁心磁致振动的影响

为研究退火处理对非晶合金磁特性及非晶铁心振动的影响,采用磁特性测量设备对退火前非晶带材及退火后非晶铁心的磁化特性和磁致伸缩特性进行了测量,基于测量数据建立了非晶合金卷形铁心磁-机械多物理场耦合模型,计算得出退火前后两种状态铁心各处的磁通密度分布及振动情况,并与样机振动测量数据进行了比较。结果表明:退火可提高非晶合金饱和磁感应强度,改善磁导率,并可减小磁致伸缩系数,从而有效地抑制变压器铁心的振动。     

Resonance modes of two-layer exchange-coupled ferromagnetic film

Ferromagnetic and spin-wave resonances in two-layer exchange-coupled ferromagnetic films have been investigated numerically at different intensities of a magnetic field when it is directed in parallel or perpendicular to the film plane. Layers of the film have finite thicknesses and possess anisotropy of the easy-plane and easyaxis types. It has been shown that at a nonzero parameter of interlayer exchange coupling the dynamic component of magnetization upon ferromagnetic resonance is distributed nonuniformly across the film thickness. Its change has been described when the external magnetic field decreases from the saturating field to zero.     

Interaction of the surface of ribbons of amorphous soft-magnetic iron-based alloys with water and their magnetic properties

The effect of interaction of the surface of ribbons of amorphous soft-magnetic alloys with water on the magnetization distribution and magnetic properties has been investigated on the example of ribbons of amorphous rapidly quenched alloys Fe₈₁B₁₃Si₄C₂ and Fe₇₇Ni₁Si₉B₁₃. It has been shown by these investigations that the interaction of the surface of ribbons of amorphous silicon-containing soft-magnetic iron-based alloys with water leads to a reduction in the maximum magnetic permeability. The decrease in μ_max is caused by a magnetization redistribution in the plane of the ribbon, namely, by an increase in the volume of domains with an in-plane magnetization oriented transversely to its axis. This is connected with the formation in this direction, due to a locally directed ordering, of an enhanced concentration of atoms incorporated into the ribbon surface and inducing a pseudo-uniaxial tension that favors a reorientation of the magnetization. The degree of changes in the magnetic properties depends on the temperature of water.     

Calculation of cooling rate of amorphous aluminum alloy melt-spun ribbons

Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapid solidification process of amorphous ribbons prepared by melt spinning was approximately modeled by one-dimensional heat conduction equation. Besides, integration with the temperature gradient, the relationship between the ribbon thickness and solidification time was derived according to the boundary conditions of ribbon-copper wheel. A simply theoretical model was obtained to calculate the cooling rates of aluminum amorphous ribbons. According to the above theoretical model, the critical cooling rate of aluminum amorphous ribbons by melt spinning is above 10^6 K/s, which proves that the aluminum based alloys belong to the marginal glass forming ability of alloys. The calculated results are in good agreement with other estimated values reported previously.     

Influence of annealing environment on microstructure and magnetic properties of amorphous Co75Fe5Zr10B10 ribbons

Rapidly solidified amorphous Co₇₅Fe₅Zr₁₀B₁₀ ribbon has been subjected to heat treatment at temperature of 300 °C for 10 min under three different atmospheric conditions, such as; air, vacuum and hydrogen-blowing atmospheres. Although no significant change in bulk structure of the ribbons was observed through X-ray diffraction analysis, substantial changes in surface microstructures are seen through SEM microstructural investigations. It is observed that the magnetic softness (coercivity, initial permeability, longitudinal permeability ratio [(Δμ/μ)%], sensitivity factor of (Δμ/μ)%, etc.) of the hydrogen-blowing atmospheric annealed ribbons is enhanced, compared to the as quenched, air and vacuum annealed samples. Moreover, a comparative study between these low temperature annealed samples has been reported.     

Magnetic properties and the giant magnetic impedance of amorphous ribbons of an FeCoCrSiB alloy after small plastic deformation

Processes of magnetization and magnetic impedance (MI) effect have been investigated for the amorphous ribbons of the Fe₃Co₆₇Cr₃Si₁₅B₁₂ alloy with various degrees of small plastic deformation (from 0 to 1%). The dependence of the total impedance and of the active and reactive resistances measured by using the probing current of frequency f = 10 MHz and strength I _rms = 1.5 mA are analyzed together with the induction hysteresis loops. Under the effect of small deformation, the coercive force and the saturation field increase and the shape of the hysteresis loop becomes somewhat more complex, indicating some changes in the processes of magnetization with increasing role of rotation processes. The magnitude of MI effect and its hysteresis decrease with increasing degree of plastic deformation. The maximum values of the relative change in the active resistance turn out to be higher than the maximum values of the relative change in the total impedance. Small plastic deformations make it possible to controllably change the position of the maximum of the magnetic impedance in an external field and to expand the region of the working fields of MI materials.     

Magnetic properties and large magnetocaloric effect in Gd-Ni amorphous ribbons for magnetic refrigeration applications in intermediate temperature range

Amorphous Gd_68−xNi_32+x (x = −3, 0, 3) ribbons were prepared by melt-spinning method. The crystallization onset temperatures T_x1 for Gd_68−xNi_32+x amorphous ribbons with x = −3, 0, and 3 are 561, 568, and 562 K, respectively. All the samples undergo the second-order magnetic transition at temperatures between ∼122 (x = −3 and 3) and 124 K (x = 0). The Curie temperature T_C does not change with the composition significantly. The maximum isothermal magnetic entropy changes (−ΔS_M)_max of Gd₇₁Ni₂₉, Gd₆₈Ni₃₂, and Gd₆₅Ni₃₅ amorphous ribbons for a magnetic field change of 0-5 T were 9.0, 8.0, and 6.9 J kg⁻¹ K⁻¹, respectively. Large values of the refrigerant capacity (RC) were obtained in these ribbons. For example, Gd₇₁Ni₂₉ amorphous ribbon has a maximum RC value of 724 J kg⁻¹. Large magnetic entropy change and RC values together with high stability enable the Gd₇₁Ni₂₉ amorphous alloy a competitive candidate among the magnetic refrigeration materials working at temperatures near 120 K.     

Surface condition monitoring of unalloyed steel sheet by measuring ferromagnetic properties and using multi-parameter data analysis

Initial investigations into coated steel sheets were conductted to verify whether sample- and batch-independent classification of surface condition can be achieved with multi-inductive data acquisition and multivariate data analysis without using a priori information. Using an ‘integrated sensor’ - a multi-inductive sensor - it is possible to obtain parameters of eddy currents, hysteresis and noise voltage with PC control. These parameters are the input values of multivariate data analysis.     

Effect of parameters of heat treatment on magnetic properties and magnetization distribution in ribbons of amorphous soft magnetic iron-based alloys

The effect of the isothermal-holding temperature and cooling rate upon in-air heat treatment on the magnetic properties and magnetization distribution in ribbons of amorphous soft magnetic iron-based alloys with positive saturation magnetostriction has been investigated. The results of the investigation showed that the dependence of the maximum magnetic permeability on the isothermal-holding temperature correlates with the corresponding changes in the magnetization distribution in the ribbon and is determined by diffusion processes that occur upon in-air heat treatment at a specific isothermal-holding temperature. An increase in the cooling rate leads to an ambiguous effect on the level of magnetic properties. The increase favors an improvement in magnetic properties when, after in-air heat treatment, either a predominantly amorphous state of the surface or a state with the formed amorphous-crystalline surface layer with a nearly optimal thickness is obtained.     

The role of tensides in the covering, formation and power loss properties of amorphous metallic ribbons by glassy coatings

Tensides are surface active substances which play an essential role in the formation of glassy coatings from aqueous solutions of H₃BO₃, H₃PO₄ and their salts. Firstly, they ensure the wettability of the hydrophobic metallic ribbon at the phase boundary in very low concentrations and, in addition, they adjust both specifically and effectively the reaction conditions between the depositing solution and the surface of the amorphous metallic ribbon. They penetrate into the interlayer of the ribbon changing its physico-chemical properties and in this way influence its magnetic characteristics. This paper deals with the effect of commercially produced non-ionic tensides (Slovanik NT, Slovasol EL, Slovasol O) and an anionic tenside (Slovafos 3) in the process of the formation of glassy coatings vs. power loss for amorphous Fe₈₂Si₆B₁₂, Fe₄₀Ni₄₀B₂₀ and Co₇₀Fe₅Si₇B₁₈ ribbons. The influence of different amounts of tensides in borate and phosphate deposition solutions and of heat treatment of these solutions on power loss is discussed.