Metallic Ribbons Research Articles

High density of shear bands and enhanced free volume induced in Zr70Cu20Ni10 metallic glass by high-energy ball milling

High-energy ball milling was employed to induce plastic deformation of Zr70Cu20Ni10 metallic glass ribbons, resulting in intersected and branched shear bands with a minimal spacing of about 30nm. Crystallization was not observed in the shear bands. The free volume content in the deformed metallic glass increases with increasing duration of ball milling. Compared with the as-spun metallic glass, 28.8% more free volume is introduced in the metallic glass after ball milling for 80h.

Magnetic properties of current-annealed amorphous thin films

An annealing technique based on electrical current heating is extended from the case of metallic ribbons to thin films, by taking into account the role of thermal dissipation played by the film substrate. It has been employed in order to study the evolution of the magnetic properties with increasing annealing current intensity, and thus annealing temperature, of amorphous Fe-Co-Nb-Si-P-B thin films. Results are compared with conventionally annealed samples, treated in furnace at similar temperatures. Joule heating turns out to be more effective in softening the magnetic properties of the studied alloy in thin film form, with respect to furnace annealing. Additionally, Joule heating (performed at low current intensities) is able to promote the development of a spin reorientation transition in the studied film, which results in the appearance of a transcritical hysteresis loop and a dense stripe domain configuration.

Symmetries and the conductance of graphene nanoribbons with long-range disorder

We study the conductance of graphene nanoribbons with long-range disorder. Due to the absence of intervalley scattering from the disorder potential, time-reversal symmetry (TRS) can be effectively broken even without a magnetic field, depending on the type of ribbon edge. Even though armchair edges generally mix valleys, we show that metallic armchair nanoribbons possess a hidden pseudovalley structure and an effectively broken TRS. In contrast, semiconducting armchair nanoribbons inevitably mix valleys and restore TRS. As a result, in strong disorder metallic armchair ribbons exhibit a perfectly conducting channel, but semiconducting armchair ribbons exhibit ordinary localization. TRS is also effectively broken in zigzag nanoribbons in the absence of valley mixing. However, we show that intervalley scattering in zigzag ribbons is significantly enhanced and TRS is restored even for smooth disorder if the Fermi energy is smaller than the potential amplitude. The symmetry properties of disordered nanoribbons are also reflected in their conductance in the diffusive regime. In particular, we find suppression of weak localization and an enhancement of conductance fluctuations in metallic armchair and zigzag ribbons without valley mixing. In contrast, semiconducting armchair and zigzag ribbons with valley mixing exhibit weak localization behavior.

Synthesis, Characterization, and Studies of Coordination-Polymeres With Isomeric Pyridylcyanoximes: Route to Metal Ribbons With Very Short Tl···Tl Separations

Two isomeric pyridylcyanoximes, H(3PCO) and H(4PCO), containing nitrogen atoms of the heterocycle at 3- and 4-positions, respectively, were synthesized and thoroughly characterized using IR (including 15N labeling), UV–visible, 1H,13C one- and two-dimensional NMR spectroscopy, and X-ray analysis. The H(3PCO) exists as a mixture of syn- and anti-isomers in solutions, contrary to H(4PCO) which is present only as an anti-isomer. Both compounds have planar geometry in the solid state and form elegant zigzag chains via H-bonding between the oxime group and the N-atom of the heterocycle. The H(3PCO) and H(4PCO) upon addition of a base form colored conjugated and solvatochromic anions in solutions. The reaction of the hot aqueous solution of Tl2CO3 with solid isomeric pyridylcyanoximes leads to TlL, which were characterized by elemental analyses, IR spectroscopy, and X-ray analysis. Both complexes represent three-dimensional coordination polymers of different complexities where cyanoxime anions act as bridging ligands. Thallium(I) atoms in Tl(3PCO) and Tl(4PCO) form infinite, planar “metal ribbons” with unusually short intermetallic distances: 3.705 Å in Tl(3PCO) and 3.635 Å in Tl(4PCO) respectively, which are close to that in metallic thallium (3.465 Å). The latter compound has the second shortest Tl···Tl thallophillic interaction reported in the literature thus far. Both yellow Tl(3PCO) and orange Tl(4PCO) are insulators at ambient conditions: R ∼ 1 × 1011 Ohm.

Corrosion resistance of bonding zone of AISI 316L–304 stainless steels joined with iron based glass ribbon interlayer: microstructural effects

The effect of holding time on the microstructure and corrosion resistance of the junction zone of AISI 316L bonded to AISI 304 stainless steels (SSs) at 960°C using an Fe based alloy filler was investigated. Samples of austenitic SSs were joined in a sandwich-like arrangement using non-commercial Fe60Ni12Cr8P13B7 metallic glass ribbon. Microstructural analysis revealed significant dissolution of the amorphous ribbon in both SSs for short holding times, exhibiting a narrow interlayer with very fine precipitates. Larger holding times induced widening of the interlayer and coarsening of γ precipitates in the iron based alloy and significant variation of the interlayer chemical composition. Microstructural dissimilarity of the bonding zone promoted selective dissolution coupled with crevice corrosion of the joints in 3·5 wt-% sodium chloride solution. In general, at the joining temperature of 960°C, the bonding ribbon and the AISI 316L SS presented higher corrosion resistance as the holding time increased up to 20 min.

Effects of Composition Changes on Strength, Bend Ductility, Toughness, and Flex-Bending Fatigue of Iron-Based Metallic Glass Ribbons

Vickers microhardness, nanohardness, tension tests, notch and fatigue precrack toughness tests, and controlled monotonic and cyclic strain experiments via bending over mandrels of different diameter have been performed on two different chemistries of Fe-based (Fe-Si-B) metallic glass ribbons. The tensile strengths of Fe73.5Cu1Nb3Si13.5B9 were 2000 ± 100 MPa and 1640 ± 35 MPa for Fe78Si9B13, which is consistent with the microhardness trends. High notch toughness (e.g., 89 ± 0.9 MPam1/2 - Fe73.5Cu1Nb3Si13.5B9; 94.5 ± 5.5 MPam1/2 - Fe78Si9B13) and fatigue precracked toughness of 76 MPam1/2 for the Fe73.5Cu1Nb3Si13.5B9 and 80 MPam1/2 for the Fe78Si9B13 were obtained. Flex-bending cyclic fatigue tests revealed a fatigue limit of 385 MPa for Fe78Si9B13 ribbons, whereas the more brittle behavior of the Fe73.5Cu1Nb3Si13.5B9 ribbons prevented the generation of flex-bending fatigue data. These results are discussed in the light of recent work on metallic glass systems.

Variation of Hardness and Modulus across the Thickness of Zr-Cu-Al Metallic Glass Ribbons

ABSTRACTWe investigate through-thickness hardness and modulus of Zr50Cu45Al5 metallic glass melt-spun ribbon. Because of their thinness, the ribbons are challenging to measure, so we employ a novel nanoindentation based-method to remove artifacts caused by ribbon flexing and edge effects. Hardness and modulus vary approximately linearly across the thickness but, unlike bulk ingots, the side of the ribbon that cooled most quickly had the highest hardness and modulus. This “inverse” variation may be caused by the fast-moving solidification front, which might conceivably, for instance, push free volume in advance of it. Annealing near Tg causes both hardness and modulus to increase and become more uniform across the thickness.

The precipitation of nanocrystalline structure in the joule heated Fe72Al5Ga2P11C6B4 metallic glasses

In this study, the evolution of the nanostructure on dc Joule heated Fe72Al5Ga2P11C6B4 metallic glass ribbons have been investigated. Heating power per square area (PS) was ranging between 0.8 to 7.1 W/cm2 in order to get various stages of relaxation or nanocrystallization. The crystallization starts after applying PS ? 4.35 W/cm2 and the sample consist of residual amorphous matrix, a magnetic crystalline component and also a non-magnetic crystalline component (relative abundance of Fe in the crystalline phase is about 35 %). XRD measurements show that crystalline samples after current annealing consist of Fe3B, FeC, FeP and Fe3P compounds. On TEM micrograph a broad distribution of shapes and sizes is noticed, the latter range from about 60 to 350 nm, increasing by applied heating power. The decrease of the electrical resistivity after each current annealing treatment is rather small in comparison with other Fe-based amorphous alloys (only about 1.5 % for the highest PS). Partial nanocrystallization leads to increase of coercive field (from HC ? 7 A/m in the amorphous as-cast state up to 45 A/m) attributed to precipitation of magnetically harder compounds (Fe3B and FeC).

Ultrasonic Bonding of Aluminum Ribbons to Interconnect High-Efficiency Crystalline-Silicon Solar Cells

Next-generation, crystalline-silicon solar cells might use different metallization concepts compared to current state-of-the-art cell designs. One specific design uses a thin aluminum back layer created with a physical vapor deposition process. In the solar industry, there is no reliable, cost-effective method of directly connecting metallic ribbons to such an aluminum layer to create cell strings. In the semiconductor industry ultrasonically bonding aluminum ribbon to the aluminum metallization of power semiconductors or high-volume production is a well-established process. This paper describes adapting ultrasonic ribbon bonding and the equipment used in the semiconductor industry to interconnect crystalline-silicon solar cells.

Conductivity anisotropy of assembled and oriented carbon nanotubes

An assembly of packed and oriented rodlike particles exhibit anisotropic physical properties. We investigate in the present work the anisotropic conductivity of films made of intrinsically conducting rods. These films are obtained from more or less ordered carbon nanotube liquid crystals. Their orientational order parameter is measured by polarized Raman spectroscopy. A relationship between the anisotropy of surface conductivity and orientational order parameter is determined. The experimental results are accounted for by a model that takes into account the number of intertube contacts and density of conductive pathways in different directions, as introduced by J. Fischer et al. for magnetically aligned nanotubes. We find that a good agreement, without any fitting parameter, of the proposed model and experiments is obtained when we consider a two-dimensional (2D) Gaussian distribution of the nanotube orientation. The conductivities parallel and perpendicular to the nematic director differ by almost an order of magnitude. This anisotropy is much greater than that of conventional dielectric liquid crystals, where the behavior is governed by the mobility anisotropy of ionic current carriers. The present results do not depend on the intrinsic properties of the nanotubes and are expected to be relevant for other assemblies of conducting rodlike particles, such as metallic or semi-conducting nanowires and ribbons.

Studying nearest neighbor correlations by atom probe tomography (APT) in metallic glasses as exemplified for Fe40Ni40B20 glassy ribbons

A next nearest neighbor evaluation procedure of atom probe tomography data provides distributions of the distances between atoms. The width of these distributions for metallic glasses studied so far is a few Angstrom reflecting the spatial resolution of the analytical technique. However, fitting Gaussian distributions to the distribution of atomic distances yields average distances with statistical uncertainties of 2 to 3 hundredth of an Angstrom. Fe40Ni40B20 metallic glass ribbons are characterized this way in the as quenched state and for a state heat treated at 350°C for 1h revealing a change in the structure on the sub-nanometer scale. By applying the statistical tool of the χ2 test a slight deviation from a random distribution of B-atoms in the as quenched sample is perceived, whereas a pronounced elemental inhomogeneity of boron is detected for the annealed state. In addition, the distance distribution of the first fifteen atomic neighbors is determined by using this algorithm for both annealed and as quenched states. The next neighbor evaluation algorithm evinces a steric periodicity of the atoms when the next neighbor distances are normalized by the first next neighbor distance. A comparison of the nearest neighbor atomic distribution for as quenched and annealed state shows accumulation of Ni and B. Moreover, it also reveals the tendency of Fe and B to move slightly away from each other, an incipient step to Ni rich boride formation.

Application of Fe-based metallic glasses in wastewater treatment

► We found the Fe-based metallic glasses have potential application in wastewater treatment. ► The corrosion on the surface of Fe-based metallic glasses is related to the application. ► We set a new theory to explain the process of degredation organic metters with Fe-based metallic glasses. This work pioneered the use of the Fe 78 Si 9 B 13 metallic glass ribbons in wastewater treatment. Fe 78 Si 9 B 13 metallic glass was employed to remediate wastewater contaminated with a mixture of organic dyes. The removal rate of chemical oxygen demand (COD) with Fe 78 Si 9 B 13 metallic glass and metallic Fe 0 was up to 23 ± 0.93% in 30 min and 21 ± 0.67% with in 45 min, respectively. The dosage of Fe-based metallic glass was only 1/25 of that of metallic Fe 0 to obtain equivalent effects. The mechanism of wastewater treatment through Fe-based metallic glasses is discussed.

Development of the Large Scanning Mirror Using Fe-Based Metallic Glass Ribbon

In order to achieve the large scanning angle without mechanical failure during actuation, the micro-mirror structure was fabricated using Fe-based metallic glass (MG) ribbon. High values of mechanical strength and elastic strain limit are desired for the torsion bar for providing high performance of the mirror, including large tilting angle and good stability. MG materials guarantee superior value of elastic strain limit and fracture toughness resulting from its amorphous structure without line defects like dislocations and grain boundaries. We chose Fe-base MG material for mirror actuation according to its good soft magnetic properties and simple structure without any further step of integration of magnetic material. Millimeter-size mirror device was successfully fabricated by laser machining techniques from Fe-based MG ribbon. Extremely large optical tilting angle of exceeding 100° was obtained on activation of the mirror by magnetic force when electrical current of 100 mA was applied. Large tilting angle of the mirror is due to the torsion bar which was fabricated with Fe-based MG material that has large elastic strain limit and high fracture toughness.

Development of the Large Scanning Mirror Using Fe-Based Metallic Glass Ribbon

In order to achieve the large scanning angle without mechanical failure during actuation, the micro-mirror structure was fabricated using Fe-based metallic glass (MG) ribbon. High values of mechanical strength and elastic strain limit are desired for the torsion bar for providing high performance of the mirror, including large tilting angle and good stability. MG materials guarantee superior value of elastic strain limit and fracture toughness resulting from its amorphous structure without line defects like dislocations and grain boundaries. We chose Fe-base MG material for mirror actuation according to its good soft magnetic properties and simple structure without any further step of integration of magnetic material. Millimeter-size mirror device was successfully fabricated by laser machining techniques from Fe-based MG ribbon. Extremely large optical tilting angle of exceeding 100° was obtained on activation of the mirror by magnetic force when electrical current of 100 mA was applied. Large tilting angle of the mirror is due to the torsion bar which was fabricated with Fe-based MG material that has large elastic strain limit and high fracture toughness.

Hydrogen-Storage Properties of Nanocrystalline Mg-Based Materials Created through Controlled Devitrification of a Metallic Glass

Mg-based nanostructured materials with a composition of Mg85Ni15-xMx (M=Y, La, or Pd) have been fabricated by proper alloying additions and controlling the crystallization process of melt spun metallic glass ribbon. XRD suggests that the average crystallite sizes range from 100 nm in the binary materials to <30 nm in the ternary alloys. Hydrogen absorption/desorption measurements show improved properties compared to nanocrystalline alloys fabricated using other processing strategies. Surface treatment of the binary and Pd-containing ribbons by ball milling or submersion in aqueous NH4+ allows the materials to be activated at 473 K, significantly lower than conventional Mg-based hydrogen storage materials. Y and La additions improve the maximum storage capacity. Absorption kinetics are also improved the materials is alloyed with La, while Y slows the reaction kinetics. Some degradation in storage capacity is observed when the materials are exposed to a cyclic absorption/desorption process, likely due to microstructural coarsening. The Mg85Ni10Pd5 composition fully absorbs and desorbs ≈5 wt. % H at 473 K, while other bulk Mg-based materials require temperatures in excess of 573 K.

A study of phase separated Ni66Nb17Y17 metallic glass using atom probe tomography

Microstructural characterization of Ni(66)Nb(17)Y(17) as spun metallic glass ribbon was carried out using atom probe tomography. A comparison of different experimental conditions for pulsed laser and pulsed voltage field evaporation reveal that the laser pulsing can be optimized to avoid preferential evaporation of yttrium. Atom probe tomography measurements illustrate that the sample undergoes phase separation resulting in two interconnected phases during the process of vitrification. The yttrium-enriched phase was depleted in niobium and yttrium-depleted phase was enriched in niobium. Moreover, detailed analyses of the roller-contact and non-contact sides of the melt-spun ribbon show different wavelength of phase separated regions revealing that the degree of phase separation is directly associated with the cooling rate.

Development of a slow-wave MEMS phase shifter on CMOS technology for millimeter wave frequencies

We propose a slow-wave MEMS phase shifter that can be fabricated using the CMOS back-end and an additional maskless post-process etch. The tunable phase shifter concept is formed by a conventional slow-wave transmission line. The metallic ribbons that form the patterned floating shield of this type of structure are released to allow motion when a control voltage is applied, which changes the characteristic impedance and the phase velocity. For this device a quality factor greater than 40 can be maintained, resulting in a figure of merit on the order of 0.7dB/360° and a total area smaller than 0.14mm2 for a 60-GHz working frequency.

Shaping of metallic glasses by stress-annealing without thermal embrittlement

Thermomechanical shaping of metallic glasses has previously been reported to result in severe thermal embrittlement. This phenomenon is most likely the reason why little effort has been made to exploit the mechanical properties of complex shapes attainable by thermomechanical shaping of metallic glass tapes and ribbons. The present study revealed time–temperature windows in which metallic glasses can be shaped by thermal annealing while remaining fully ductile. These include binary (Fe 83B 17, Co 80B 20 and Pd 82Si 18), ternary (Fe 81.5B 14.5Si 4 and Cu 60Zr 30Al 10) and more complex quaternary Zr 70Ni 16Cu 6Al 8 glassy alloys of both metal–metalloid and metal–metal types. All showed full bending ductility after shaping. The thermomechanical processing leading to full shaping without thermal embrittlement was successfully modeled using the approach of A.I. Taub ( Acta Metallurgica 1981) based on the free-volume model of structural relaxation. The results are of direct interest for applications of metallic glasses as springs.

Boron and Nitrogen Doping Induced Half-Metallicity in Zigzag Triwing Graphene Nanoribbons

The electronic and magnetic properties of quasi-1D zigzag triwing graphene (ZZ-TWG) ribbons with boron and nitrogen (BN) doping were investigated by means of a spin-polarized density functional theory approach. Our results showed that asymmetric BN doping can give rise to half-metallicity and suppress spin polarization of the doped wings, making the BN-doped ZZ-TWGs potential application in spintronics devices. Heavily doping can turn metallic ZZ-TWG ribbons into semiconductors. A critical ratio of BN to C and appropriate doping site (e.g., ribbon’s edges) are required for achieving specific electronic properties. An effective path of engineering electronic properties of ZZ-TWGs by BN doping was suggested.

Detecting density variations and nanovoids

A combination of simulated and experimental data has been used to investigate the size range of nanovoids that can be detected in atom probe tomography data. Simulated atom probe tomography data have revealed that nanovoids as small as 1 nm in diameter can be detected in atom probe tomography data with the use of iso-density surfaces. Iso-density surfaces may be used to quantify the size, morphology and number density of nanovoids and other variations in density in atom probe tomography data. Experimental data from an aluminum-yttrium-iron metallic glass ribbon have revealed the effectiveness of this approach. Combining iso-density surfaces with atom maps also permits the segregation of solute to the nanovoids to be investigated. Field ion microscopy and thin section atom maps have also been used to detect pores and larger voids.