Thin Ribbons Research Articles

Influence of the grain size on the martensitic transformation and strain nanodomains in the Ti-Hf-Ni-Cu shape memory alloy

The martensitic transformation and strain nanodomain were studied in the Ti40.7Hf9.5Ni44.8Cu5 shape memory alloy, whose grain size varied from 130 μm to 160 nm. The largest average grain size (600 μm in length and 130 μm in diameter) was found in the CAST sample. The grains with the smallest size (160 nm) formed during the crystallisation of thin ribbons obtained by the melt spinning technique from the Ti40.7Hf9.5Ni44.8Cu5 ingot (labelled as RIBBON). The average grain size (16 μm) was observed in the sample subjected to high-pressure torsion and post-deformation annealing (labelled as HPT). It was found that the CAST and HPT samples included the NiTi-based matrix and the Ti2Ni-type precipitates, whereas the RIBBON sample contained the NiTi-based matrix only. Regardless of the grain size, all samples underwent the B2 ↔ B19’ transformation on cooling and heating. A decrease in grain diameter from 130 μm to 160 nm decreased the transformation temperatures by more than 100 °C but did not affect the sequence of the transformation. The strain nanodomains formed in all samples on cooling prior to the forward martensitic transformation. The smaller the grain size, the larger the temperature range of the strain nanodomain existence. On heating of HPT and RIBBON samples, the B19 phase transformed to the B2 phase with strain nanodomains, which disappeared only on heating over 120 °C. The influence of grain size on the martensitic transformation and strain nanodomains was analysed from the thermodynamics approach.

Optimization of Planar Flow Melt Spinning Process for Producing Thin, Wide, and Continuous Amorphous Ribbons of Fe73.5Si13.5B9Nb3Cu1 Alloys

Optimization of Planar Flow Melt Spinning Process for Producing Thin, Wide, and Continuous Amorphous Ribbons of Fe73.5Si13.5B9Nb3Cu1 Alloys

Buckling of planar curved beams with finite prebuckling deformation

The serpentine structure with a sufficiently thick cross section has recently been proposed as an important design concept in stretchable electronics, which features mechanically stable in-plane deformation mechanism and very low electrical resistance, bringing unique advantages for devices compared with the traditional thin ribbon layout. However, unduly increasing the thickness is well known to sacrifice the overall flexibility and functionality of devices. Such a contradiction leads to challenges in structural stability, as a relatively thick but insufficient serpentine structure may eventually undergo the out-of-plane buckling after significant in-plane prebuckling deformation and appreciable alterations in initial configuration, which is ignored by most conventional buckling theories (CBTs) and linear buckling analysis in commercial finite element analysis software, producing intolerable errors when predicting the critical loads. In this paper, a systematic and straightforward theory considering the finite prebuckling deformation (FPD buckling theory) is established to investigate the underlying mechanism. Two sets of governing equations related to the prebuckling and FPD buckling behavior are obtained. Four representative examples, including two classical problems of planar curved beams and two typical loading conditions of serpentine structures, have been carefully studied. Comparisons with the accurate geometrically-nonlinear-analysis-based (GNAB) buckling analysis have amply demonstrated the validity of our theory in predicting the reinforcement effect of prebuckling deformation on the buckling resistance of structures. Key dimensionless geometric parameters that govern this effect have also been identified, providing direct and effective guidance for the design and optimization of stretchable electronic devices.

Improving the surface characteristics of metallic glass thin ribbons by laser gas nitriding

The single-roll cooling method excels in producing metallic glass ribbons (MGRs), offering rapid cooling rates and exceptional thickness consistency. Nevertheless, a large number of defects including micro-pits and micro-gaps usually appear on the surface of MGRs after the roll forming process, significantly impacting their service life and performance. Laser gas nitriding is a cutting-edge surface modification technology that has been extensively used to improve the comprehensive performance of various metal components. Herein, an attempt was made to simultaneously improve the surface quality and mechanical properties of Zr41.2Ti13.8Cu12.5Ni10Be22.5 MGRs by nanosecond pulsed laser irradiation in a flowing nitrogen atmosphere. The effects of laser irradiation parameters on the surface characteristics of the laser gas nitrided regions were systematically investigated. The experimental results showed that the surface quality of MGRs after laser gas nitriding was enhanced, accompanied by a simultaneous improvement in hardness and scratch resistance. This study underscores laser gas nitriding as a potent strategy to augment the comprehensive surface characteristics of MGRs. This enhancement is poised to significantly extend their service life and reinforce their reliability when utilized as structural and functional materials in sectors such as machinery, national defense, and aerospace.

Effect of Cu addition on the properties of Pd-based metallic glasses by experimentation and molecular dynamics simulations

The effect of trace Cu element additions on the properties of Pd-based amorphous alloys was investigated by a combination of experimental and molecular dynamics (MD) simulations. Thin ribbons of Pd40Ni40P20 and containing different proportions of Cu (1 %, 3 %, and 5 %) were prepared, analyzed by X-ray diffraction (XRD) to determine the phase structure, tested for their thermal properties by differential scanning calorimetry (DSC), and nanoindentation to test their mechanical properties. Meanwhile, the amorphization process and compression behavior of these alloys were simulated by MD simulation, and the microstructures of the alloys were resolved by using the radial distribution function (RDF) and the coordination number distribution function (PDF), and the glass transition temperatures (Tg) were deduced from the energy variations. The Voronoi polyhedral analyses showed that the addition of trace amounts of Cu altered the content of the specific clusters, which affected the macroscopic mechanical properties. Both nanoindentation experimental and simulation results confirmed that the addition of trace Cu reduces the Tg and improved the mechanical properties of the Pd40Ni40P20 alloy while maintaining the amorphous structure.

MERCI: Mixed curvature-based elements for computing equilibria of thin elastic ribbons

Thin elastic ribbons represent a class of intermediary objects lying in-between thin elastic plates and thin elastic rods. Although the two latter families of thin structures have received much interest from the Computer Graphics community over the last decades, ribbons have seldom been considered and modelled numerically so far, in spite of a growing number of applications in Computer Design. In this paper, starting from the reduced developable ribbon models [Sadowsky 1929; Wunderlich 1962] recently popularised in Soft Matter Physics, we propose a both accurate and efficient algorithm for computing the statics of thin elastic ribbons. Inspired by the super-clothoid model for thin elastic rods, our method relies on compact ribbon elements whose normal curvature varies linearly with respect to arc length s , while their geodesic torsion is quadratic in s . In contrast however, for the sake of efficiency, our algorithm avoids building a fully reduced kinematic chain and instead treats each element independently, gluing them only at the final solving stage through well-chosen bilateral constraints. Thanks to this mixed variational strategy, which yields a banded Hessian, our algorithm recovers the linear complexity of low-order models while preserving the quadratic convergence of curvature-based models. As a result, our approach is scalable to a large number of elements, and suitable for various boundary conditions and unilateral contact constraints, making it possible to handle challenging scenarios such as confined buckling experiments or Möbius bands with contact. Remarkably, our mixed algorithm proves an order of magnitude faster compared to Discrete Elastic Ribbon models of the literature while achieving, in a few seconds only, high accuracy levels that remain out of reach for such low-order models. Additionally, our numerical model can incorporate various ribbon energies, including the RibExt model for quasi-developable ribbons recently introduced in Physics [Audoly and Neukirch 2021], which allows to transition smoothly between a rectangular Kirchhoff rod and a (developable) Sadowsky ribbon. Our numerical scheme is carefully validated against demanding experiments of the Physics literature, which demonstrates its accuracy, efficiency, robustness, and versatility. Our Merci code is publicly available at https://gitlab.inria.fr/elan-public-code/merci for the sake of reproducibility and future benchmarking.

Rapidly solidified Al-Cu-Co quasicrystalline alloy: microstructure and catalytic properties

This study presents the characterisation and evaluation of the catalytic potential of an alloy with a composition referring to the quasicrystal from the Al-Cu-Co system. The material was synthesised through a melt-spinning process, providing rapid solidification conditions and a favourable material form of thin ribbons. Microstructural and chemical analyses were performed using scanning electron microscopy, X-ray diffraction and transmission electron microscopy methods. The obtained results confirmed the presence of a major phase which was a decagonal quasicrystal in the form of globular grains and additional crystalline phases occurring along the grain boundaries. The catalytic potential of the materials was explored using phenylacetylene hydrogenation. The catalyst, obtained by pulverising the ribbons, demonstrated catalytic activity with over 40% phenylacetylene conversion and selectivity exceeding 60% for styrene production under mild reaction conditions. The recovered catalyst displayed a stable phase composition, as confirmed by X-ray diffraction, and unchanged morphology, indicating the possibility of catalyst reuse for subsequent reaction cycles. The presented results provide insight into the experimental verification of the catalytic properties of the developed environmentally friendly catalysts.

Extraordinary Polarization and Thickness Dependences of Photocarrier Dynamics in PdSe2 Ribbons.

Pentagonal palladium diselenide (PdSe2) stands out for its exceptional optoelectronic properties, including high carrier mobility, tunable bandgap, and anisotropic electronic and optical responses. Herein, we systematically investigate photocarrier dynamics in PdSe2 ribbons using polarization-resolved optical pump-probe spectroscopy. In thin PdSe2 ribbons with a semiconductor phase, the photocarrier dynamics are found to be dominated by intraband hot-carrier cooling, interband recombination, and the exciton effect, showing weak crystalline orientation dependences. Conversely, in thick semimetal-phase PdSe2 ribbons, the photocarrier relaxations governed by the electron-optical/acoustic phonon scattering strongly depend on the sample orientation, albeit with a degradation in in-plane anisotropy following hot-carrier cooling. Furthermore, we analyze the correlations between photocarrier dynamics and anisotropic energy dispersions of electronic structures across a wide range in k space, as well as the contributions from the anisotropic electron-phonon couplings. Our study provides crucial insights for developing polarization-sensitive photoelectronic devices based on PdSe2.

Electrical Resistivity of Lead-Free Solders Reinforced by Carbon Nanospheres

Electrical resistivity of the nanocomposites Sn96.5Ag3Cu0.5 and Sn95,5Ag3,8Cu0,7 lead-free solder alloys with minor admixtures of carbon nanospheres (0.05 wt%) was measured in a wide temperature range, including a melting-solidification region. Influence of the carbon nanospheres content on electrical resistivity values has been analyzed. Carbon nanospheres were obtained by electrical discharge method from diesel fuel, cyclohexane, and aviation kerosene. The matrix samples were produced by planar flow casting technique in the form of thin ribbons. Electrical resistivity measurements were performed using four-probe method. Hysteresis between the heating and cooling electrical resistivity curves relates to the non-equilibrium solidification.

Non-Isothermal Analysis of the Crystallization Kinetics of Amorphous Mg72Zn27Pt1 and Mg72Zn27Ag1 Alloys.

In this study, thin ribbons of amorphous Mg72Zn27Pt1 and Mg72Zn27Ag1 alloys with potential use in biomedicine were analyzed in terms of the crystallization mechanism. Non-isothermal annealing in differential scanning calorimetry (DSC) with five heating rates and X-ray diffraction (XRD) during heating were performed. Characteristic temperatures were determined, and the relative crystalline volume fraction was estimated. The activation energies were calculated using the Kissinger method and the Avrami exponent using the Jeziorny-Avrami model. The addition of platinum and silver shifts the onset of crystallization towards higher temperatures, but Pt has a greater impact. In each case, Eg > Ex > Ep (activation energy of the glass transition, the onset of crystallization, and the peak, respectively), which indicates a greater energy barrier during glass transition than crystallization. The highest activation energy was observed for Mg72Zn27Pt1 due to the difference in the size of the atoms of all alloy components. The crystallization in Mg72Zn27Ag1 occurs faster than in Mg72Zn27Pt1, and the alloy with Pt has higher (temporary) thermal stability. The Avrami exponent (n) values oscillate in the range of 1.7-2.6, which can be interpreted as one- and two-dimensional crystal growth with a constant/decreasing nucleation rate during the process. Moreover, the lower the heating rate, the higher the nucleation rate. The values of n for Mg72Zn27Pt1 indicate a greater number of nuclei and grains than for Mg72Zn27Ag1. The XRD tests indicate the presence of α-Mg and Mg12Zn13 for both Mg72Zn27Pt1 and Mg72Zn27Ag1, but the contribution of the Mg12Zn13 phase is greater for Mg72Zn27Ag1.

Mesoscale polymer arrays: high aspect ratio surface structures and their digital reconstruction.

Inspired by adhesive bio-filamentous structure, such as bacterial pili, this work details the methods used to fabricate and characterize a surface-anchored array of thin, flexible and shape-responsive mesoscale polymer ribbons with a length-to-thickness aspect ratio of up to 100 000. The resulting structures exhibit geometrically complex and dynamic morphologies consistent with elastocapillary bending that experience an increase in curvature over hours of aging due to creep. We develop a computational image analysis framework to generate 3D reconstructions of these densely crowded geometries and extract quantitative descriptors to demonstrate morphological changes due to aging. We demonstrate the robustness of this quantitative method by characterizing the creep-induced change in an aging ribbon array's shape and develop a scaling relationship to describe the importance of ribbon thickness for shape and dynamical observations. These methods demonstrate an essential baseline to probe morphology-property relationships of mesoscale polymer ribbon arrays fabricated from a variety of materials in numerous environments. Through the introduction of perfluorodecalin droplets, we illustrate the potential of these ribbon arrays towards applications in adhesive, microrobotic, and biomedical devices.

Microstructure and Air Trace Defects of the Rapidly Solidified ZK60 Magnesium Alloy Ribbon.

ZK60 alloy metal ribbons were prepared successfully in a carbon dioxide atmosphere by varying the speeds of melt spinning. The thin metal ribbon with different solidification speeds was prepared by controlling different rotation speeds, and the influence of solidification speed on the ZK60 ribbon was studied. The results show that the gas mark has a significant effect on the local structure of the ribbon. The gas mark's proportional area of the ZK60 ribbon increases first and then decreases with the increase in roll speed, and the gas mark proportion area is the smallest at 17.6 m/s. With the increase in the solidification rate, the base texture of the ribbon is enhanced, and the proportion of columnar crystals in the ribbon gradually increases. At the rate of 17.6 m/s, columnar crystals run through the entire side of the ribbon, and uniformly distributed spherical-particle phases are found inside the grain. At the speed of 17.6 m/s, the mechanical properties of different areas of the ribbon are close and different from those of the other two speeds, and the performance of the quenching zone is better than that of the slow-cooling zone.

Stability of the B2 ↔ B19′ martensitic transformation on thermal cycling of Ti-Hf-Ni-Cu thin ribbons

The B2 ↔ B19′ martensitic transformation was studied on thermal cycling of the Ti40.7Hf9.5Ni49.8-xCux (x = 5, 10 at.%) thin ribbons. The temperatures, as well as the enthalpy of the transformation, were found to be stable on thermal cycling. The stability of the B2 ↔ B19′ transformation was attributed to the formation of a specific grain structure during the crystallization of the initially amorphous ribbons. The grains were characterized by an average size of 800 nm, which increased the yield limit for dislocation slip to 700 MPa. Moreover, one martensite corresponding variant pair (CVP) formed on cooling inside each grain. It was assumed that the formation of one CVP martensite plate within the grain on cooling, as well as a high yield limit for dislocation slip, might have been responsible for the stability of the martensitic transformation temperatures and enthalpy on thermal cycling.

A Study of Root Canal Morphology of Human Deciduous Maxillary Molars using Cone Beam Computed Tomography (CBCT): An in Vivo Study

Aim: The purpose of this study was to investigate the root canal morphology of the primary maxillary right first and second molars using CBCT according to Vertucci & New root canal classification system given by Ahmed HMA et al., Method: 60 Patients aged 3-9 years were taken in the study. The CBCT of maxillary right quadrants of study subjects were taken at imaging centre and evaluated on CBCT scans according to Vertucci & Ahmed HMA et al.,’s classification both. Result: The most common canal configuration for right primary maxillary 1st and 2nd molar was Vertucci Type I except mesio-buccal canal in right maxillary second molar was Vertucci Type IV. Conclusion: As deciduous molar teeth exhibit thin torturous canals and ribbon like roots a thorough knowledge of the root canals can improve the outcome of pulp treatment in pediatric patients.

Computational model of twisted elastic ribbons.

We develop an irregular lattice mass-spring model to simulate and study the deformation modes of a thin elastic ribbon as a function of applied end-to-end twist and tension. Our simulations reproduce all reported experimentally observed modes, including transitions from helicoids to longitudinal wrinkles, creased helicoids and loops with self-contact, and transverse wrinkles to accordion self-folds. Our simulations also show that the twist angles at which the primary longitudinal and transverse wrinkles appear are well described by various analyses of the Föppl-von Kármán equations, but the characteristic wavelength of the longitudinal wrinkles has a more complex relationship to applied tension than previously estimated. The clamped edges are shown to suppress longitudinal wrinkling over a distance set by the applied tension and the ribbon width, but otherwise have no apparent effect on measured wavelength. Further, by analyzing the stress profile, we find that longitudinal wrinkling does not completely alleviate compression, but caps the magnitude of the compression. Nonetheless, the width over which wrinkles form is observed to be wider than the near-threshold analysis predictions: the width is more consistent with the predictions of far-from-threshold analysis. However, the end-to-end contraction of the ribbon as a function of twist is found to more closely follow the corresponding near-threshold prediction as tension in the ribbon is increased, in contrast to the expectations of far-from-threshold analysis. These results point to the need for further theoretical analysis of this rich thin elastic system, guided by our physically robust and intuitive simulation model.

Giant exchange bias in the nanostructured MnAl thin ribbons

In this study, Mn54Al46 thin ribbons composed of nanostructured ferromagnetic and antiferromagnetic phases were fabricated by a melt spinning method, and a tunable exchange bias field was obtained by precisely controlling the wheel speed and the cooling field. The x-ray diffraction result confirms the existence of the nanostructured Mn-poor ε phase. The pinned ferromagnetic Mn-poor ε phase coupled with the antiferromagnetic Mn-rich ε phase accounts for the exchange bias observed in the sample fabricated at a wheel speed of 65 m/s in which almost no τ phase is formed. Furthermore, the exchange bias field first increases and reaches the most significant reported value of 41 kOe in this system and then decreases with the increase in the cooling field, exhibiting an inversely proportional relationship with the magnetization. The decrease in the exchange bias field is believed to be related to the increased coupling thickness of the ferromagnetic phases with the increase in the cooling field.

Lichenometric Analysis Applied to Bedrock Fault Scarps: The Sencelles Fault and the 1851 CE Mallorca Earthquake (Balearic Islands, Spain)

The Sencelles Fault constitutes the main extensional structure of Mallorca Island (Spain), holds a NE-SE orientation, and has been identified as the possible seismic source of the 1851 CE Palma earthquake (VII EMS.) The SE termination of the fault (Sta. Eugenia Segment) features a linear bedrock fault scarp of a maximum of 3.15 m height. The last 840 m of this rocky scarp display a significant horizontal banding, with up to five differentially weathered ribbons colonized by lichens. The lichenometric analysis is based on the measurement of 155 specimens of Aspicilia calcarea (Ac) and Aspicilia radiosa (Ar) in tombstones and funerary monuments (with inscribed dates) from the nearby cemeteries of Sta. María del Camí, Sta. Eugenia and Sencelles, to obtain the local lichen growth rates (LGR), with the two last graveyards being directly located in the fault zone. Lichens were measured on variously oriented (N, S, NE, SW, etc…) horizontal and vertical surfaces, generating differentially oriented lichen populations (DOLPs) to be compared with the Ac and Ar specimens colonizing the studied fault scarp (38 measured individual specimens). After successive trial and error regression tests, vertical DOLPs resulted in the best appropriate groups for the analysis, with LGR of 0.23–0.31 mm/yr. Horizontal ones reached widths of up to 20 cm, with LGR up to 0.84 mm/yr, which were clearly oversized. The application of the selected LGR points to a human-induced origin for the thin basal lichen ribbon of the scarp (10–13 cm), which should have developed during the middle 20th century (c. 1950–1966) because of documented ground leveling works. However, the second ribbon of the scarp (23–47 cm) shows exposure dates of 1852 ± 40 (Ar) and 1841 ± 59 (Ac), overlapping the date of the 1851 CE earthquake. The study is complemented with data from a fault trench excavated in the year 2002 at the toe of the scarp. The combined data of lichenometry, fault trenching, and the length of the analyzed fault scarp (c. 840 m) indicate that the studied segment of the fault cannot be considered a co-seismic surface faulting related to the 1851 CE event as a whole, but a relevant secondary earthquake effect on a pre-existing fault scarp (e.g., sympathetic ground ruptures).

A Study on the Aesthetic Characteristics of Hetaira Beauty Style Expressed in Greek Pottery

This study studied the aesthetic characteristics of Hetaira's costume and beauty style expressed in pottery paintings of the Greek era as the contents of Greek mythology were recently re-examined as the subject of humanities interest. In ancient Greece, the common name for prostitutes was Hetaira, and she was a religious prostitute who was at the top of the list of prostitutes in Greek society, enjoying the wealth of freedom and status more than any other woman. The aesthetic characteristics of the Hetaira beauty style of the Greek era were largely shown as An ornament beauty, An ostentatious sensuality and symbolic beauty of power. First, An ornament beauty was the makeup of a Greek Hetaira woman, who emphasized her eyes with thick and dark black eyebrows and black eyeliner. The Hetaira woman's face was white with white lead, her eyes were emphasized with eyeshadow using black cowl, and she applied orange short yarn to her cheeks and mouth to put on intense color makeup. Hetara dyed her hair in all sorts of colors, decorated her hair with hairpieces, wore thin cloth ribbons and chest bands, and sprayed perfume made with special prescriptions. Second, ostentatious sensual beauty was applied to various sexual zones of the feminine body and the whole body, such as the nipple and buttocks, which can stimulate men's sexual pleasure, and Hetair's outfit was in the form of a full-body keyton or revealing the upper body. The hair was as voluminous as possible, and the method of dispersing the tarae on the forehead was used to make it look as sensual as possible. Curled hair with thick waves was naturally curled up and expressed sensibly using a signon shape and long hair. Third, the symbolic beauty of power is that ancient Greece's ‘privilege fashion’ was ‘nature’, a power that only men could have, but Hetaira had equal power with men in the symposium with nakedness. The hairstyle seems to have been able to wear a veil or a laurel crown, which is exclusively for men. In the form of a wig, he preferred a curling style with no forehead exposed, and it was found that he produced blade hair. Hetaira's style, represented in Greek pottery paintings, had hair, makeup, and fashion styles that represented the Greek era, possessed greater power and wealth than ordinary women in the Greek era, and was found to have the privilege of wearing heavy makeup, light hair colors and hair decorations that were not allowed by ordinary women. Therefore, it was found that it was very meaningful to study Hetaira's beauty style in studying the beauty culture of the Greek era.

Dimension reduction analysis of a three-dimensional thin elastic plate reinforced with fractal ribbons

AbstractThe aim of this paper is to study the dimension reduction analysis of an elastic plate with small thickness reinforced with increasing number of thin ribbons developing fractal geometry. We prove the$\Gamma $-convergence of the energy functionals to a two-dimensional effective energy including singular terms supported within the Sierpinski carpet.

On the Helical Crystals of Cholesterol Monohydrate

We review in this short perspective the history of cholesterol crystals and crystal structures. We address in particular the helical crystals that form in vitro and in pathology from environments rich in bile acids or from phospholipid membranes. We review the known mechanisms leading to crystals with chiral morphology, from screw-dislocation mediated growth to mechanisms involving asymmetric mechanical strain. We propose a mechanism for cholesterol helical crystal development based on the monoclinic cholesterol monohydrate crystal structure. We suggest that curvature arises in few layers thick crystals due to the tension induced between the hydrophobic layer and the ice-like H-bonded lattice of the water molecules with the cholesterol hydroxy groups. Helicity would ensue through a combination of the curvature and the fast growth of a thin ribbon in one crystal direction.