Thick Ribbons Research Articles

Biological tissue for transcatheter aortic valve: The effect of crimping on fatigue strength

Transcatheter aortic valve replacement (TAVR) has become today the most attractive procedure to relieve patients from aortic valve disease. However, the procedure requires crimping biological tissue within a metallic stent for low diameter catheter insertion purpose. This step induces specific stress in the leaflets especially when the crimping diameter is small. One concern about crimping is the potential degradations undergone by the biological tissue, which may limit the durability of the valve once implanted. The purpose of the present work is to investigate the mechanical damage undergone by bovine pericardium tissue during compression and analyze how this degradation evolves with time under fatigue testing conditions. Pericardium 500 μm thick pericardium ribbons (5 mm large, 70 mm long) were crimped down to 12 Fr for 30 and 50 min within a metallic stent to replicate the heart valve crimping configuration. After crimping, samples underwent cyclic fatigue flexure and pressure loading over 0.5 Mio cycles. Samples were characterized for mechanical performances before crimping, after crimping and after fatigue testing in order to assess potential changes in the mechanical properties of the tissue after each step. Results bring out that the ultimate tensile strength is not modified through the process. However an increase in the modulus shows that the crimping step tends to stiffen the pericardium. This may have an influence on the lifetime of the implant.

Elucidation of annealing effects on austenite–martensite and magnetic phase transitions in Mn2Ni1.6Sn0.4 ribbons synthesized from bulk alloys prepared by RF induction melting

We investigate the consequences of annealing on the structure, microstructure, magnetic, and electrical transport of Mn2Ni1.6Sn0.4 ribbons. The 40–60 μm thick ribbons were formed by melt spinning of the bulk ingot synthesized by RF induction melting. Ribbons were annealed at 600 °C for 12 hrs and the other at 800 °C for 2 hrs in vacuum. All ribbons crystallize into a cubic symmetry (space group F4¯3m). The orthorhombic phase appears as the secondary one. In ribbons annealed at 600 °C, the crystallite size decreases from ∼ 47 nm to ∼ 29 nm, and annealing at 800 °C doubles the crystallite size to ∼ 96 nm. The least amount of microstrains (17x10−4) in the as-synthesized ribbon is consistent with the occurrence of the superlattice peaks (111) and (200). Lower intensities of the superlattice peaks in 600 °C and 800 °C ribbons are consistent with higher microstrains (25x10−4 and 24x10−4). Hence, a higher degree of Ni-Mn ordering improves magnetic properties in annealed samples. The as-synthesized ribbon has an austenite-phase Curie temperature of TCA∼303K, which enhances to TCA∼320K and TCA∼310K after annealing at 600 °C and 800 °C. The ribbon annealed at 600 °C has the highest saturation moment. All the ribbons show the exchange-bias (EB) effect, and the most pronounced effect is seen in the 800 °C annealed ribbon. Microstructure uniformization and relative strengths of the Ni-Mn and Mn-Mn interactions improve the magnetics. Near TC, MT=M0TC-Tβ is satisfied (β = 0.31, 0.36, and 0.37, for as-synthesized, 600 °C and 800 °C annealed ribbons). The low-temperature spontaneous magnetization obeys the Bloch law MT=M01-AT32, with a deviation in 600 °C annealed ribbon due to spin freezing. The ρ-T has been fitted in the different temperature ranges using the various combinations in ρT=ρ0+AphT+BsdTα. At T < 85 K, the resistivity of the as-synthesized ribbon follows ρT=ρ0+BsdTα, with α≈1.47, while for the 600 °C annealed ribbon, α≈1.49. The exponent α∼1.5 supports the existence of the spin glass state in the lower temperature region of as-synthesized and 600 °C annealed ribbons. In the high-temperature range, the linear ρ-T behavior is described by ρT=ρ0+AphT and consistent with the electron–phonon scattering.

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.

Production and characterization of amaranth amyloid fibrils from food protein waste

Plant proteins self-assembly into amyloid fibrils is a promising modification to be introduced in emerging food and materials applications. Although the valorization of protein-rich side streams in amaranth oil production is completely missing, we show that double salt extraction provides the recovery of globulin fraction of amaranth seed from food waste with high purity and complete protein solubility at acidic pH. We demonstrate in silico the self-assembly propensity with a high density of amyloidogenic regions of the 11S seed storage globulin of Amaranthus hypochondriacus. We further show that the recovered amaranth proteins can self-assemble into amyloid fibrils under heat-induced acidic hydrolysis. The amyloid nature of the fibrils was studied by thiazole orange (TO) fluorescence, SDS-PAGE, FTIR, CD, TEM, and AFM. We systematically investigated how the temperature of fibrillization affected protein unfolding, peptide release, as well as its effect on tuning the formation, growth, and polymorphism of amaranth amyloid fibrils. The β-sheet-rich structured proteins produced from the amaranth food waste exhibited mesoscopic polymorphism of the rigid amyloid fibrils with the manifestation of left-handed ribbons of varying polymorphism. We show that favourable conditions for extensive hydrolysis of the amaranth proteins promote the growth of well-ordered thick twisted ribbons with small-pitch and extraordinary rigidity and we interpret these finding based on structural mesoscopic models of amyloid fibrils. These results provide additional insight into the formation of plant amyloid fibrils as functional food and biocompatible materials, and introduce a pathway to convert amaranth food protein waste into amyloid nanofibrils.

Bearded capuchin monkey as a model for Alzheimer’s disease (AD) research

AbstractBackgroundThe absence of a natural animal model is one of the main challenges to research in AD. AD‐type pathology has been described in chimpanzees and other primates’ brains. The bearded capuchin monkey (Sapajus libidinosus) is a New World primate that attracted attention mainly due to its skill in creating and using tools. We evaluated the brains of three captive capuchins (9, 29 and 33 years‐old) who died from natural causes at the Primate Center of University of Brasilia.MethodWhole brain was fixed in 4% buffered paraformaldehyde within 12 hours of death for three weeks. Structural 7T MRI was acquired in one case before brain slicing. Consecutive coronal sections from the fixed brain were embedded in paraffin, and 5um sections from paraffin blocks were used for staining and immunohistochemistry evaluation. All brain sections were stained with hematoxylin and eosin. Immunohistochemistry with β‐amyloid (4G8), phosphorylated tau (AT8), p62, TDP‐43, α‐synuclein (81A), 68 kDa neurofilament (2F11), GFAP and CD68 antibodies were performed in selected sections to analyze the following areas: frontal cortex, temporal cortex, parietal cortex, occipital cortex, anterior cingulate cortex, hippocampus, amygdala, basal ganglia, thalamus, mesencephalon, pons, medulla oblongata, and cerebellum.ResultMacroscopic evaluation of the brains showed considerable cortical gyrification. In addition, thick cortical ribbon was observed in the MRI. A complete neuropathological evaluation was available for two cases. Widespread β‐amyloid immunoreactivity was observed in the form of diffuse deposits, core‐space‐corona plaques, perivascular plaques, and amyloid angiopathy. A high frequency of classic neuritic plaques was observed. P‐tau antibody failed to label the dystrophic neurites. However, these lesions were revealed with p62 and neurofilament antibodies. Astrocyte hypertrophy surrounding plaques was observed without microglial activation. Very few hyperphosphorylated tau aggregates resembling neurofibrillary tangles and neuropil threads were found in the temporal and frontal cortex, and Lewy‐type and TDP‐43 pathology were not observed.ConclusionIn summary, we found β‐amyloid immunoreactivity, classic neuritic plaques surrounded by astrocyte hypertrophy, but only rare P‐tau aggregates. To our knowledge, this is the first evidence reporting brain AD‐like alterations in capuchin monkeys which suggest that this species can be considered an advantageous animal model for AD research.

Extracting quartz deformation fabrics from polymineralic rocks

Quartz dynamic recrystallization fabrics are the record of deformation temperatures, strain rates, and fluids, and can be qualitatively and quantitatively evaluated using optical microscopy and electron backscatter diffraction (EBSD). Characterization of quartz deformation fabrics have been largely guided by textures in homogenous monomineralic samples. However, in nature such lithological homogeneity is uncommon, and mica and feldspar that interrupt the interconnectedness of quartz inhibit the exchange of material across quartz grain boundaries, effectively pinning these grains and preventing dislocation creep.We present two EBSD methods of extracting quartz domains within polyphase mylonites to investigate the effects of discontinuous quartz distribution and remove isolated quartz grains pinned by other phases. These samples provide textural evidence for grain boundary migration in quartz at temperatures exceeding 500 °C. Quartz domains vary in size from cm thick foliation parallel continuous ribbons, to isolated quartz grains separated by networks of mica and feldspar. We quantify contrasting textural responses to deformation between connected and isolated quartz grains using existing measures of EBSD data analysis, including M-index, grain orientation spread, kernel averaged misorientation, and grain size. We find that removing isolated quartz grains yields pole figures that are more representative of the regional deformation.

Fabrication and soft magnetic properties of FeSiB based flakes with insulating surface layer suitable for high frequency power applications

FeSiB based soft magnetic flakes (SMFs; ϕ: 63-106 µm, t: 2-5 µm) coated with optimally thick (∼10 nm) SiO2 were fabricated as the potential magnetic material for pressed cores suitable for use in power inductors operating beyond 10 MHz. Such thin SMFs were produced by mechanical ball milling of commercially available thick (∼27 µm) ribbons followed by an optimized sol-gel coating in presence of a silane coupling agent. Milling helped to reduce ribbon thickness below the skin depth to minimize eddy current loss at high frequencies. The effect of milling (medium, duration, rotation speed, and ball-to-powder ratio) and coating conditions on the soft magnetic properties of the SMFs were investigated. An optimally tiny fraction of the milled flakes was allowed to become nanocrystalline, which augments saturation flux density (BS) and permeability (µ) without incurring additional losses. The results from X-Ray photoelectron spectroscopy and magnetization measurement confirm that a stress-releasing post-annealing process reduced coercivity from ∼62 Oe to ∼6 Oe and enhanced the magnetic saturation moment from 126 emu/g to 142 emu/g without affecting the thin yet robust insulating SiO2 layer.

Nanoporous Copper Ribbons Prepared By Chemical Dealloying of a Melt-Spun Zn-Cu Alloy

Dealloying process is a powerful and versatile method to fabricate three-dimensional nanoporous (np) materials for applications in electrochemical synthesis, sensors, and catalysis. In the last years, several morphologies of np-copper and their dealloying mechanisms have been reported in alkaline and acidic media.[1-4] For instance, the nature of anions such as chloride and phosphate strongly influence the ligament size of np-Cu. The effects of several experimental parameters to control the structural and chemical properties of np-Cu materials via dealloying are not fully understood to date.In our work, Zn80Cu20 alloy ribbons prepared by melt-spinning were dealloyed by free corrosion in 0.1 M HCl and 1.3 M NaOH solutions. Both the surface and cross-section of the obtained np-Cu ribbons were comprehensively characterized by SEM, EDX, STEM, XRD, and XPS. Our results show a clear relation between dealloying conditions (pH, kind of electrolyte and reaction time) and structural parameters (ligament size and chemical composition) for np-Cu ribbons. The ligament size is strongly coupled with the residual Zn content prepared by dealloying in acidic environment. In contrast, the ligaments produced in alkaline media are much smaller, whereas the residual Zn content can be tuned in a broad range without changes in ligament size. For the first time, we point out the distribution of residual Zn within single ligaments of np-Cu. We suggest that the Cu surface atoms diffuse and capture the Zn atoms which are located in the near-subsurface during dealloying. Therefore, the Zn-rich regions seem to be relicts of the master alloy. We have also evaluated the time-resolved evolution of porosity within the ribbons via cross-section analysis. Despite the relatively thick melt-spun ribbons (35 ± 3 μm), kinetics of a bicontinuous ligament-pore structure are controlled by the interfacial process instead of the diffusion of corrosive electrolyte solution in and out of the porous layers, referred to as long-range mass transport. Surface diffusivities of Cu at 25 °C were determined to be 1.4 × 10−18 and 9.4 × 10−21 m2 s−1 in 0.1 M HCl and 1.3 M NaOH, respectively. Therefore, the high Cu surface diffusion rate in the presence of chloride ions enables an enhanced dealloying front propagation into the ribbons, and also coarsening of the ligaments to form larger ligament. On the contrary, the slow surface diffusion rate of Cu (hydr)oxide in 1.3 M NaOH solution strongly limits the dealloying process and forms smaller ligaments. Moreover, dealloying temperature strongly influences the surface diffusivity of Cu, leading to a strong relationship between dealloying temperature and the np-Cu structure. The electrochemically active surface area of np-Cu ribbons was determined by double layer capacity method. The catalytic properties of the np-Cu ribbons were then evaluated for organic electro-synthesis of cyclic carbonates from CO2 and epoxide. The yield of cyclic carbonate could be improved by using np-Cu ribbons for the activation of CO2.Based on our results, we provide deeper insights to the formation processes of np-Cu ribbons with tunable ligament size and Zn content in various electrolyte environments and its application as electrode material for electro-synthesis of cyclic carbonates formation from CO2 and epoxide.

Minimum Quench Energy of Nb3Sn Wires With High Specific Heat Tape

A major problem of state-of-the-art Nb$_3$Sn accelerator magnets is their long training due to thermo-mechanical perturbations. Increasing the specific heat, $C_p$, of the Rutherford cable would reduce and/or eliminate training by limiting the coils temperature rise. This paper studies feasibility of increasing the $C_p$ of Rutherford-type cables by using thin composite Cu/$Gd_2$O$_3$ and Cu/$Gd_2$O$_2$S tapes produced by Hyper Tech Research, Inc. The tape can be either wrapped around the cable, placed on the cable wide faces under the insulation, and/or inserted as a core. Wire samples outfitted with these high-$C_p$ ribbons, or tapes, were prepared and tested at FNAL for their Minimum Quench Energy (MQE). At 90%I$_c$ and 15 T, the average gain of MQE of the Nb$_3$Sn wire soldered to the Cu/$Gd_2$O$_2$S 55 micrometer thick ribbon was 2.5, and further increased at larger transport currents.

Microstructure and properties of ultra-thick Fe-based metallic glass by twin-roll strip casting versus a traditional process

In this study, an ingenious twin-roll strip casting approach is described to process large-size Fe71Ni9P12B4.9Si2.5Cu0.6 amorphous ribbons. The 150 μm thick RT ribbon (novel process) characterized by a completely amorphous structure is 5 to 7 times thicker than the conventional Fe-based RS (conventional process) ribbon. The minimum cooling rates of the RS and RT ribbon were 1.78 × 106 and 5.58 × 105 K/s. The RT ribbon's excellent thermodynamic properties led to fine grain size and a high magnetic induction of 1.63 T. However, high internal stress led to a large magnetocrystalline anisotropy. The hardness of the two ribbons was similar at ∼1160 Hv. Moreover, the significant size effect led to a slight decrease in the fracture toughness of the RT ribbon. The impressive specifications, high impurity tolerance, and good properties of the RT ribbon render twin-roll strip casting promising for industrial applications.

Applications of generalized integral transform technique in the rapid solidification of metallic metals in the planar flow casting process / Aplicações da técnica de transformação integral generalizada na solidificação rápida de metais metálicos no processo de fundição em fluxo planar

The Planar Flow Casting (PFC) is a single-stage fast solidification technique to produce thin metallic ribbons. The objective of this research is to develop a mathematical model to analyze the phenomenon of heat transfer and phase change during the formation of the puddle, to determine the interface position and velocity and the temperature profile. The applied methodology consists of the use of the energy balance, where the equations of the energy (liquid and solid phases), and the equation of the interface are transformed through the Generalized Integral Transform Technique (GITT) being solved by the NDSolve routine of the Matemathica. This tool was capable to solve problem, can study the fast cooling of metals and obtain ribbons of thickness controlled by the speed of the wheel and for the heat transfer coefficient. Considering that the height of the pool is very small and the process time is very short, many eigenvalues were used to obtain the solution convergence. The results of the temperature distribution along the length of the puddle, the evolution of the solidification front and the interface velocity were compared with existing results in the literature, obtaining good harmony.

Plastic Zr-Al-Ni-Cu-Ag bulk glassy alloys containing quasicrystalline or β-Zr plus ω-Zr phases

Zr70–76Al7–7.5Ni13–15Cu2Ag2–5 glassy alloys were prepared by melt-spinning with Zr contents up to 76 at.%, greatly exceeding the highest Zr content of 70 at.% previously reported for Zr-based glassy alloys exhibiting a calorimetric glass transition. The 70–72Zr and 74Zr alloys were also cast as bulk rods up to 1.5 mm in diameter with glass and [glass + β-Zr + ω-Zr] phases, respectively, by ejection copper-mold casting. The crystallization temperature and Vickers hardness Hv for the glassy ribbons decrease with increasing Zr content from 70 to 76 at.%. The glassy rods show high yield strength (σy) of 1225–1346 MPa, high fracture strength (σf) of 1497–1499 MPa, and large compressive plastic strain (εp) of 9.7–3.2% for the 70–72Zr alloys. Similarly, the 74Zr rod with [glass + β-Zr + ω-Zr] phases shows σy of 1325 MPa, σf of 1472 MPa, εp of 2.4%. The 76Zr thick ribbon with [glass + β-Zr + ω-Zr] phases shows, in tension, high σy of 890 MPa, σf of 988 MPa, and plastic elongation of 0.3%. The Zr-rich glassy ribbons crystallize, showing three exothermic peaks upon heating. The first-stage peak is due to the precipitation of icosahedral quasicrystal (IQ) for the 70–72Zr ribbons, and β-Zr + ω-Zr for the 74–76Zr ribbons. These annealing-induced mixed-phase ribbons with Zr content above 72 at.% exhibit good bending plasticity, even though their HV is about 41% higher than for the as-spun glassy ribbons. Similarly, the 70Zr bulk rod, with [glass + IQ] phases obtained by annealing, shows a distinct increase in σy and σf to 1485 and 1575 MPa, respectively, as well as εp of 0.6%. Thus, the plastic Zr-rich bulk rods with glass, [glass + IQ], and [glass + β-Zr + ω-Zr] phase mixtures are encouraging for the future development of a new type of high-strength structural material.

Microstructure and Hard Magnetic Properties of Sm1- x Zr x (Fe,Co)11.3- y Ti0.7B y Ingots and Thick Melt-Spun Ribbons

Permanent magnets made from Sm(Fe,Co) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> -based compounds are being actively pursued through nanostructuring and powder metallurgy. This study was aimed at the development of hard magnetic properties in bulk as-cast alloys and in melt-spun alloys for very low wheel speeds. Slower solidification rates and alloying with Zr promote the tetragonal ThMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> -type crystal structure, whereas higher solidification rates and alloying with B replace the ThMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> structure type with the TbCu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> structure type. When introduced simultaneously, Zr and B dramatically reduce the alloy solidification rates required for both the refinement of the 1:12 crystallites and their replacement with the 1:7 phase. In bulk arc-melted alloys, this allowed for a microstructure of separated 1:12 crystallites 1– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3~\mu \text{m}$ </tex-math></inline-formula> in size, although, because of the ferromagnetic nature of a minority phase, the coercivity of these fine-grained alloys reached only 0.73 kOe. A moderately accelerated solidification further refined the 1:12 crystallites and increased the coercivity; a Sm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> (Fe,Co) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10.8</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> alloy exhibited a coercivity of 1.5 kOe and a maximum energy product of 3.4 MGOe when it was melt-spun into a 0.26 mm-thick ribbon. A more rapid solidification suppressed the 1:12 phase, and after annealing at 800 °C–850 °C, the alloys modified with Zr and B developed reasonably high coercivity and maximum energy product even when melt-spun at a wheel speed of 6 m/s. For the above-mentioned alloy, these values were 4.1 kOe and 7.8 MGOe, respectively. A similarly processed very-Sm-lean Sm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> (Fe,Co) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10.6</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> alloy exhibited a remanence of 8.8 kG and an energy product of 7.4 MGOe.

A Cryogenic Hydrogen Ribbon for Laser Driven Proton Acceleration at Hz-Level Repetition Rate

We report on recent progress in deploying a continuous solid hydrogen ribbon as a debris-free and renewable laser-driven source of pure proton beams generated by a 30-fs laser with ∼1-J laser energy focused on target at relativistic intensities of ∼1019 W/cm2 and repetition rate of 0.1 Hz. The stability of the ribbon position versus the laser interaction point and maximum repetition rate was tested up to 3.3 Hz. The acceleration of protons with cut-off energies up to 1.5 MeV is demonstrated using a 100-μm thick hydrogen ribbon as proof-of-principle capability of the relatively thick target delivery system. The laser-target geometry presented demonstrates an experimental technique that can potentially enables the operation of a laser–plasma source at Hz-level repetition rate.

Воздействие ионного облучения (Аr+, E = 15-20 кэВ) на микроструктуру деформированного сплава Ni - 13.9 мас.% W

Using X-ray diffraction analysis, the effect of Ar+ ions with an energy of 15-20 keV (at ion current densities of 100-300 μA/cm2) on the microstructure, the level of internal microstresses and the texture of cold rolled ribbons of alloy Ni-13.9 wt.% W was studied. It was found that short-term irradiation of 80 μm thick ribbons with a fluence of 3.1·1016 cm-2 (for 50 s) at temperatures T ≤ 370°C and T = 630°C leads to a decrease in microstresses in their entire volume, but at the same time the original texture is retained. With an increase in the fluence to 9.7·1017 cm-2 at T = 630°C, the texture also changes from (220) to (200). Changes in microstresses and texture on the irradiated and unirradiated sides of 80-μm-thick ribbons are comparable to each other, despite the fact that the projective range of Ar+ ions with an energy of 15-20 keV in the alloy is only ~7 nm. It is known that annealing in an oven (700°C, 30 min) of such ribbons does not lead to their recrystallization. At 850°C, microstresses are relieved and the texture drastically changed from (220) to (200) both as a result of annealing in a furnace (15 s) and as a result of irradiation with a fluence of 3.2·1016 cm-2 for 17 s, but the effect removal of stresses in the course of furnace annealing is 3 times lower than in the course of irradiation. Thus, the following facts have been established: 1) the occurrence of recrystallization processes in the alloy under study during irradiation at a temperature lower than the temperature of the onset of thermally activated recrystallization and 2) a higher rate of microstresses drop (and to lower values) in the course of irradiation than during furnace annealing. This indicates a significant role of nanoscale radiation-dynamic effects at the cascade-forming irradiation of metastable media.

A Predictive Model for the Anisotropy Index of Semi-Coke Derived from the Properties of Colombia's Eastern Cordillera Coals

This study developed a theoretical model for the determination of the Coke Anisotropy Quotient (CAQ) of semi-coke from the properties of its precursor coal. This is an useful parameter to define the resistance and reactivity of semi-coke in the blast furnace. For 36 semi-coke samples, a textural analysis was performed alongside a fluidity test to determine the real CAQ. The main textures observed were: isotropic and circular for high volatile bituminous coals (HVB); lenticular and fine ribbons for the medium volatile bituminous coals (MVB); and medium and thick ribbons for the low volatile bituminous coals (LVB). The CAQ varied in a range from 1 to 11. A principal component analysis (PCA) and multiple regression allowed to discriminated the importance of certain coal properties, in determining the CAQ to be recognized and to estimate parameters of the mathematical model. The statistical analysis suggested that CAQ can be best predicted from the fluidity, volatile matter, and Ro of the parent coals. The veracity of this model result was then tested using a second dataset from Poland. This work optimizes the usefulness of standard datasets in the prediction of CAQ's offering a means of quality control that could be implemented in Colombian coke production.

Boride formation behaviour and their effect on tensile ductility in cast TiAl-based alloys

Boron has been used to refine the microstructures in TiAl castings, such as low-pressure turbine (LPT) blades, to improve mechanical properties. However, boride precipitates with undesirable morphologies could reduce ductility and even entirely remove the benefits of grain refinement. Boride size and morphology in variant alloys based on Ti45Al2Mn2Nb1B has found to be closely related to alloying element species and solidification conditions, leading to distinctly different boride formation behaviour. It has been shown that Hf promotes the formation of thin curvy boride flakes whilst Ta promotes the formation of thick straight boride ribbons in the studied cooling rate range. The boride crystal structure changes from TiB with the B27 structure for coarse straight boride to TiB with Bf structure for the curvy boride. Curvy borides have the strongest effect in reducing ductility, regardless of alloy composition.

Surface Magnetostriction of FeCoB Amorphous Ribbons Analyzed Using Magneto-Optical Kerr Microscopy.

Surface sensitive magneto-optical Kerr microscopy completed with the special self-made sample holder is used for studying the magneto-elastic behaviour in the surface of the as-quenched amorphous Fe73Co12B15 alloy. The 10, 5, and 3 mm wide and approximately 34 μm thick ribbons were prepared by the conventional planar flow casting process. The experimental setup allows for a simultaneous application of an external magnetic field in the directions parallel and perpendicular to the ribbon axis and of compression stress from one side of the sample, resulting in tensile stress in opposite side. The distributions of tensile stresses in the measured surface were modelled by the finite element method. The observed changes of the magnetic domains and hysteresis loop anisotropy field under applied stress are evaluated using the Becker–Kersten method. This resulted in the determination of the local surface magnetostrictive coefficient from an area of about 200 μm in diameter. The obtained values ranged between 37–60 ppm and were well comparable with the bulk value presented in the literature.

Enhancements of preparation efficiency and magnetic properties for Fe-based amorphous magnetic flake powder cores upon the adoption of a novel double-paralleled slits nozzle

The thick and brittle amorphous ribbons with the maximum thickness up to 58 μm were successfully fabricated using melt-spinning method upon the adoption of a novel double-paralleled slits nozzle (DPSN). The magnetic properties of the two magnetic flake powder cores (MFPCs) prepared from the conventional thin ribbon pulverization and the thick ribbon pulverization were analyzed and compared. Hereinto, a coupling model of fluid flow with free surface and surface tension, and heat transfer with phase transform was developed to design the slit spacing for the DPSN, and sol-gel method was employed to create SiO2 insulation layer on the surfaces of the magnetic flake powders to improve electrical resistivity. Results show that a quasi-steady-state can be reached for the puddle with the upstream and downstream menisci in crescent and slope shapes, respectively, by adopting the DPSN with slit spaces of 2.0 mm and 2.5 mm. The embrittlement process for the conventional thin ribbon can be omitted to enhance the efficiency of the powder preparation when using the thick ribbon before the ribbon pulverization. The MFPCs fabricated using the thick amorphous ribbon pulverization exhibit a higher permeability of 65.27, lower total core loss with the frequency being less than 234 kHz for Bm = 0.08 T, and a better DC-bias property of 70.97% as compared to the MFPCs made from the conventional thin amorphous ribbon pulverization. This work provides a promising approach to further development of Fe-based amorphous MFPCs with high preparation efficiency and excellent magnetic properties at the frequency below 234 kHz.

Direct measurement of the magnetocaloric effect on micrometric Ni-Mn-(In,Sn) ribbons by the mirage effect under pulsed magnetic field

In this work, we report on the direct measurement of the magnetic field induced temperature change in a series of micrometric thick ribbons of Ni-Mn-In-Sn Heusler alloys, performed with an innovative experimental technique based on the thermo-optical “Mirage Effect.” The technique combines very fast measurement time, 1 T pulsed magnetic field in the millisecond range, and contactless temperature detection. These features make the technique ideal for the characterization of thin samples with a thickness down to a few micrometers. In this work, we demonstrate this by directly measuring the magnetocaloric effect (MCE) of micrometric-thick ribbons of Heusler alloys at the Curie transition, which was tuned on a wide temperature range by varying the Sn to In ratio. The direct test of the MCE in thin samples is fundamental for the development of refrigerant elements with a large heat-transfer coefficient and for the design of solid state micro devices for cooling and energy harvesting.