Onset Transition Temperature Research Articles

Superconductivity up to 14.2 K in MnB4 Under Pressure.

The discovery of superconductivity in 3d transition-metal compounds with strong magnetism is interesting but rare. Especially for Mn-based compounds, there exist only very limited materials that show superconductivity. Here, the discovery of superconductivity is reported with an onset transition temperature up to 14.2 K in a Mn-based material MnB4, which is the highest value among the stoichiometric Mn-based superconductors. By applying high pressure, the continuous suppression of a weak semiconducting behavior and the occurrence of superconductivity after ≈30 GPa are found. With further increasing pressure, the superconducting transition temperature (Tc) is gradually enhanced and reaches the maximum onset transition value of ≈14.2K at 150 GPa. The synchrotron X-ray diffraction data reveal the unchanged monoclinic (S.G: P21/c) symmetry but an unusual crossover of the lattice parameters b and c in a certain pressure region as confirmed by the theoretical calculation. The findings show a promising way to explore high Tc superconductivity by combining the 3d-transition metal magnetic elements and light elements.

Study on Ca-doping effects and structural stability in Bi2Sr2-xCaxCuO6+δ (0 ≤ x ≤ 1.2) compounds by Rietveld refinement and high-pressure Raman spectroscopy

The lattice distortion induced by element doping is regarded as an effective approach to improve the superconductivity of Bi-based superconductors. In this study, a series of Bi2Sr2-xCaxCuO6+δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2) ceramic samples are prepared by Pechini sol-gel method. The Ca-doping effects, structural stability and superconductivity of Bi-2201 phase are studied by electron microscopy, high-pressure Raman spectroscopy, the standard four-probe technique, X-ray diffraction and Rietveld refinements. Results indicate that all samples are constituted by Bi-2201 main phase and Ca8.56Sr5.44Bi16O38 impurity. It can be determined that Ca atoms have entered Bi-2201 orthorhombic lattice and preferentially occupied the Sr-sites. When Ca atoms are introduced and high-pressure is exerted, the Bi-2201 lattice can present a relatively high structural stability. Meanwhile, the correlations between doping amount x, Cu–O–Cu bond angle (θ), carrier concentration of CuO2 planes and superconducting onset transition temperature (Tc,onset) are discussed particularly. It should be noted that the Bi-2201 lattice has the largest θ, the highest carrier concentration and the highest Tc,onset value of 84.98 K when x = 0.8.

Preparation of a/c-oriented YBa2Cu3O7−x homogeneous superconducting junctions via pulsed laser deposition

The growth orientation of YBa2Cu3O7−x (YBCO) is extremely sensitive to the growth atmosphere and the heat-treatment temperature. However, according to the existing literature, to obtain YBCO with preferred a-axis orientation, a buffer layer needs to be prepared on the substrate. In this work, YBCO films were grown via pulsed laser deposition, and the influence of N2 and O2 deposition atmospheres on the growth orientation of the YBCO films was studied. It was found that high-quality YBCO films with preferred c-axis orientation can be grown in O2 atmosphere, but it is difficult to grow a-axis-oriented YBCO films in O2 atmosphere without using a buffer layer; however, YBCO films with a high degree of preferred a-axis orientation can be grown in N2 atmosphere without using a buffer layer. Furthermore, an a/c-oriented homogeneous YBCO bilayer with c-axis orientation in the lower layer and a-axis orientation in the upper layer was prepared. X-ray diffraction and scanning transmission electron microscopy results show that the bilayer is epitaxial with a good a/c orientation, and the resistance–temperature curve shows the occurrence of two transitions at temperatures of 91 and 71 K. We believe that these temperatures correspond to the superconducting onset transition temperatures of YBCO in the c- and a-axis growth orientations, respectively. The superconducting current usually flows within the Cu–O plane. With its sudden change in the direction of the current at the interface, the homogeneous junction prepared in this work is expected to provide new ideas for the research of high-temperature superconducting junction devices.

High-Temperature (Cu,C)Ba2Ca3Cu4Oy Superconducting Films with Large Irreversible Fields Grown on SrLaAlO4 Substrates by Pulsed Laser Deposition

(Cu,C)Ba2Ca3Cu4Oy is a nontoxic cuprate superconducting material with a superconducting transition temperature of about 116 K. Recently, it was found that bulk samples of this material synthesized under high pressure hold the highest irreversibility line among all the superconductors, which is very promising for its application in the liquid nitrogen temperature field. In this work, high-temperature (Cu,C)Ba2Ca3Cu4Oy superconducting films with large irreversible fields were prepared on SrLaAlO4(00l) substrates by pulsed laser deposition. The substrate temperature during deposition proved to be the most important parameter determining the morphology and critical temperature of the superconductors, with 680 °C considered to be the optimum temperature. X-ray diffraction (XRD) results showed that the (Cu,C)Ba2Ca3Cu4Oy films prepared under optimal conditions exhibited epitaxial growth with the a-axis perpendicular to the film surface and the b- and c-axes parallel to the substrate, with no evidence of any other orientation. In addition, resistivity measurements showed that the onset transition temperature (Tconset) was approximately 116 K, the zero-resistance critical temperature (Tc0) was around 53 K, and the irreversible field (Hirr) was about 9 T at 37 K for (Cu,C)Ba2Ca3Cu4Oy films under optimal temperature. This is the first example of the successful growth of superconducting (Cu,C)Ba2Ca3Cu4Oy films on SrLaAlO4(00l) substrates. This will facilitate high-performance applications of (Cu,C)Ba2Ca3Cu4Oy superconducting materials in the liquid nitrogen temperature field.

Investigation of elevated temperature microstructural stability and tribological behavior of MoxNbTiZr refractory high-entropy alloy coatings optimized by Mo-doping

Refractory high-entropy alloys (RHEAs) possess substantial potential for applications in high-temperature environments. In this work, the structural and high-temperature properties of MoxNbTiZr RHEA coatings are optimized by Mo-doping. The results show that Mo-doping promotes the HCP phase precipitation and proliferation of nanotwins, strengthening the microhardness but weakening the fracture toughness of the coatings. Mo-doping raises the phase transition onset temperature and end temperature by reducing the bulk diffusion rate of MoxNbTiZr RHEAs. The BCC phase of Mo1.0NbTiZr HEA coating can be stabilized to at least 1300 ℃. Mo-doping in a particular range is favourable to accelerate the sintering and curing rate of the tribo-layer. The MoxNbTiZr RHEA coatings demonstrate outstanding high-temperature tribological performance before Mo content exceeds 0.6 at%.

Effect of adaptive nanocrystalline behaviors on the cavitation erosion performance of Cu47.5Zr45.1Al7.4 bulk metallic glass

Amorphous alloys have attracted much attention in the field of cavitation erosion (CE) due to their good comprehensive properties. However, due to the special amorphous structures that are difficult to characterize, their micro-response behaviors and damage mechanisms during the CE process have not been well elucidated. In this paper, advanced techniques including focused ion beam (FIB) and transmission electron microscope (TEM) were used to comparatively study the microstructure evolution and volume loss rules of Cu47.5Zr45.1Al7.4 and Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glasses (BMG) under the action of cavitation load and cavitation heat to reveal their CE mechanisms. The results showed that the absence of small atoms in Cu47.5Zr45.1Al7.4 led to a large free volume, thereby compromising its hardness, modulus, and yield strength. However, this also made it more susceptible to shear banding, which in turn enhanced its energy absorption capabilities. Although Cu47.5Zr45.1Al7.4 had a higher glass transition temperature (Tg) and onset temperature of crystallization (Tx), as well as a wider supercooled liquid phase region (ΔTx), its exothermic peak was obviously pronounced and the transformation temperature range was significantly narrower. Therefore, it is more likely to adaptively form Cu-rich nanocrystals under the action of cavitation heat. Additionally, the larger free volume in the shear band was conducive to the diffusion of atoms and the occurrence of adaptive nanocrystallization behaviors in Cu47.5Zr45.1Al7.4. These nanocrystals were able to effectively force crack deflection, thereby dissipating impact energy and delaying the fatigue spallation of the material. Consequently, Cu47.5Zr45.1Al7.4 exhibited a far longer incubation period and a noticeably lower cumulative volume loss.

Superconductivity of a new Ru-based alloy Ru3Sb1.75Sn5.25

We report the synthesis and superconductivity of a new Ru-based alloy Ru3Sb1.75Sn5.25. The single crystal and polycrystal samples were synthesized by the Sn-flux method and solid state reaction, respectively. The Ru3Sb1.75Sn5.25 crystals were characterized by powder X-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We find Ru3Sb1.75Sn5.25 crystallize in the Ir3Ge7-type structure and exhibits superconductivity with onset transition temperature Tc = 4.2 K. Density functional theory calculation on Ru3Sb1.75Sn5.25 unveils multiple peaks of density of states around the Fermi level, which may explain the emergence of superconductivity. Our study provides an example compound to explore the fascinating interplay of superconductivity, electronic band structure and paramagnetism in Ru-based superconductors.

Nanostructures of etherified arabinoxylans and the effect of arabinose content on material properties

To further our understanding of a thermoplastic arabinoxylan (AX) material obtained through an oxidation-reduction-etherification pathway, the role of the initial arabinose:xylose ratio on the material properties was investigated. Compression molded films with one molar substitution of butyl glycidyl ether (BGE) showed markedly different tensile behaviors. Films made from low arabinose AX were less ductile, while those made from high arabinose AX exhibited elastomer-like behaviors. X-ray scattering confirmed the presence of nanostructure formation resulting in nano-domains rich in either AX or BGE, from side chain grafting. The scattering data showed variations in the presence of ordered structures, nano-domain sizes and their temperature response between AX with different arabinose contents. In dynamic mechanical testing, three transitions were observed at approximately −90 °C, −50 °C and 80 °C, with a correlation between samples with more structured nano-domains and those with higher onset transition temperatures and lower storage modulus decrease. The mechanical properties of the final thermoplastic AX material can therefore be tuned by controlling the composition of the starting material.

Effects of stearic acid on the cryotolerance of the domestic cat (Felis silvestris catus) embryos

The current work aimed to study the effect of domestic cat (Felissilvestris catus) embryosin vitroexposure to saturated stearic acid (SA) and to evaluate how the change in lipid content affects the cryopreservation results. The addition of SA to the culture medium did not affect the development of cat embryosin vitrobefore cryopreservation. The total lipid amount in the SA-treated embryos was not changed as well. However, the lipid unsaturation degree was lower in embryos afterin vitroexposure to SA. Moreover, the lipid phase transition onset temperature (T*) was higher in SA-treated embryos as compared with controls. These changes of intracellular lipids unsaturation degree andT*were associated with the impairment of embryo cryopreservation effectiveness. The results obtained may be of importance for the applying Genome Resource Banking concept to the Felinae species.

Modulation of Phase Behavior and Microscopic Dynamics in Cationic Vesicles by 1-Decyl-3-methylimidazolium Bromide.

Synthetic cationic lipids have garnered significant attention as promising candidates for gene/DNA transfection in therapeutic applications. The phase behavior of the vesicles formed by these lipids is intriguing, revealing intricate connections to the structure and dynamics of the membrane. These phenomena emerge from the complex interplay between hydrophobic and electrostatic interactions of the lipids. In this study, we explore the impact of an ionic liquid-based surfactant, 1-decyl-3-methylimidazolium bromide (DMIM[Br]), on the structural, dynamical, and phase behavior of cationic dihexadecyldimethylammonium bromide (DHDAB) vesicles. Our investigations indicate that the addition of DMIM[Br] increases the vesicle size while thinning the membrane. Further, DMIM[Br] also induces substantial changes in the membrane phase behavior. At 10 and 25 mol %, DMIM[Br] eliminates the pre-transition from coagel to intermediate crystalline (IC) phase and decreases the onset temperature of the main phase transition to the fluid phase. In the cooling cycle, the addition of DMIM[Br] further induces the formation of an intermediate gel phase. This behavior is reminiscent of the non-synchronous ordering observed in the DODAB membrane, a longer-chain counterpart of DHDAB. Interestingly, at 40 mol % of DMIM[Br], the formation of the intermediate gel phase is largely suppressed. Neutron scattering data provide evidence that the addition of DMIM[Br] enhances lipid mobility in coagel and fluid phases, suggesting that DMIM[Br] acts as a plasticizer, enhancing membrane fluidity across all of the phases. Our findings infer that DMIM[Br] modulates the membrane's phase behavior and fluidity, two essential ingredients for the efficient transport of cargo, by controlling the balance of electrostatic and hydrophobic interactions.

Structural, Thermo‐Functional, and Rheological Properties of Dielectric Modified Underutilized Jicama (Pachyrhizus, spp.) Starch

AbstractIn this study, underutilized jicama starch (JS) is treated in dielectric‐heating at different power (300, 450, 600 W) and time (1, 3, 5 min), and the change in structural, thermo‐functional, and rheological properties is observed. The dielectric modification increases the water absorption (0.81–2.88 g g−1), whereas the oil absorption capacity (1.02–0.83 g g−1) and bulk density (0.52–0.39 g mL−1) are reduced as compared to native starch. Lightness (95.46–96.26) of JS non‐significantly varies with dielectric‐heating, whereas a significant effect is observed in redness (0.01–0.06) and yellowness (3.74–4.24). The apparent viscosity of all treated samples shows shear thinning behavior. All the pasting properties other than the setback and pasting temperature of dielectric treated samples are significantly (p < 0.05) decreased at higher power than control. The onset (46.50–81.67 °C), peak (64–99.23 °C), and end temperature (68.27–100.77 °C) of gelatinization transition increased, which shows better thermal stability as compared to control. The strong‐peak for the control and treated sample is observed at around 1000 cm−1 wavenumber in the Fourier transform infrared spectroscopy. The structural changes have been observed by X‐ray diffraction analysis (XRD) and scanning electron micrographs (SEM) shows shrinkage and deformation at each power and time.

Possible strain-induced enhancement of the superconducting onset transition temperature in infinite-layer nickelates

The mechanism of unconventional superconductivity in correlated materials remains a great challenge in condensed matter physics. The recent discovery of superconductivity in infinite-layer nickelates, as an analog to high-Tc cuprates, has opened a new route to tackle this challenge. By growing 8 nm Pr0.8Sr0.2NiO2 films on the (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate, we successfully raise the superconducting onset transition temperature Tc in the widely studied SrTiO3-substrated nickelates from 9 K into 15 K, which indicates compressive strain is an efficient protocol to further enhance superconductivity in infinite-layer nickelates. Additionally, the x-ray absorption spectroscopy, combined with the first-principles and many-body simulations, suggest a crucial role of the hybridization between Ni and O orbitals in the unconventional pairing. These results also suggest the increase of Tc be driven by the change of charge-transfer nature that would narrow the origin of general unconventional superconductivity in correlated materials to the covalence of transition metals and ligands.

Comparison of Gd addition effect on the superconducting properties of FeSe0.5Te0.5 bulks under ambient and high-pressure conditions

We have prepared a series of (FeSe0.5Te0.5 + xGd) bulk samples, with x = 0, 0.03, 0.05, 0.07, 0.1 and 0.2, through the convenient solid-state reaction method at ambient pressure (CSP). High gas pressure and high-temperature synthesis methods (HP-HTS) are also applied to grow the parent compound (x = 0) and 5 wt% of Gd-added bulks. Structural, microstructural, transport and magnetic characterizations have been performed on these samples in order to draw the final conclusion. Our analysis results that the HP-HTS applied for the parent compound enhances the transition temperature (Tc) and the critical current density (Jc) with the improved sample density and intergrain connections. The lattice parameter ‘c’ is increased with Gd additions, suggesting a small amount of Gd enters the tetragonal lattice of FeSe0.5Te0.5 and the Gd interstitial sites are along the c-axis. A systematic decrease of the onset transition temperature Tc is observed with Gd additions, however, the calculated Jc of these Gd-added samples is almost the same as that of the parent compound prepared by CSP. It specifies that there is no improvement of the grain connections or pinning properties due to these rare earth additions. However, Gd-added FeSe0.5Te0.5 bulks prepared by HP-HTS have revealed a slightly improved critical current density due to improved grain connections and sample density but have a lower transition temperature than that of the parent compounds.

Impact of PbO on structural, thermal, optical and gamma ray shielding behaviour of TeO2-CdO based glasses

A study was conducted to investigate the effect of an increase in the concentration of PbO on the structural, thermal, optical, and gamma ray shielding behavior of TeO2-CdO based glasses. The glasses were found to contain TeO4 and TeO3 units, as well as CdO metal oxide clusters, as indicated by the Raman spectrum. The glasses displayed minor weight loss (approximately 3%), suggesting high resistance to thermal degradation. With an increase in the concentration of PbO, the glass transition temperature (Tg), onset temperature (To), and crystallization temperature (Tc) all decreased. Additionally, the indirect band gap energy decreased from 3.497–3.337 eV as the lead oxide concentration increased. Moreover, the effects of PbO concentration on the linear attenuation coefficient (LAC) were investigated. The LAC values were found to be highest at 39.5 keV and decreased with increasing energy. As the PbO concentration increased, LAC values also increase. The Zeff displayed an inverse relationship with energy, except for an abrupt increase at 121.8 keV. The half value layer was found to be positively correlated with energy and varied with changes in PbO and CdO concentrations. The glasses demonstrated effective gamma radiation shielding properties, with the HVL remaining small even at higher energies, suggesting potential applications in industries such as medical imaging where thin shielding materials are preferred.

AC Susceptibility and Superconducting Properties of Te-Substituted TlSr<sub>2</sub>Ca(Cu<sub>2-x</sub>Te<sub>x</sub>)O<sub>7</sub>

The effect of Te substitution on TlSr2Ca(Cu2-xTex)O7 for x = 0.2, 0.3, 0.4, and 0.5 was investigated. The solid-state reaction approach was used to prepare the samples. All TlSr2Ca(Cu2-xTex)O7 samples exhibited the presence of major Tl-1212 and minor Tl-1201 phases. Further Te replacement promoted the formation of the Tl-1201 phase. All samples demonstrated metallic normal state characteristics before onset transition temperature, Tc-onset. The resistance versus temperature curve for all samples revealed that the Tc-onset was between 46 and 40 K and the zero-resistance temperature, Tc-zero was between 29 and 37 K. The measurement of AC susceptibility revealed a susceptibility superconducting transition Tc χ' ranging from 30 to 36 K. This study showed that Te substitution stabilized the Tl-1212 phase, enhanced Tc χ’ although the Tc-onset and Tc-zero were below the boiling point of liquid nitrogen.

Morphological, Functional, and Physico‐Chemical Properties of Non‐Conventional Starch Derived from Discarded Immature Apples

AbstractThe starch yield of 23–28% (db) with 35–43% amylose content is recovered from different immature apple varieties. Scanning electron microscopy reveals the presence of the dome to spherical shaped granules of 3.1–11.62 µm size. The transition temperatures, onset temperature, peak temperature, conclusion temperature, and enthalpy of gelatinization are calculated using differential scanning calorimetry (DSC) ranges between 61.62 and 64.48 °C, between 64.61 and 68.07 °C, between 68.64 and 72.37 °C, and between 4.35 and 17.49 J g−1, respectively. The water absorption capacity and oil absorption capacity of starches range between 1.036 and 1.372 mL g−1 and between 0.876 and 1.125 mL g−1, respectively. The peak viscosity of 638–1942 cP is achieved in 3.8–6.10 min at a pasting temperature of 65–71 °C. A yield stress of 10–39 Pa is sufficient to instigate the Herschel Bulkley flow. The paste of Mollie's Delicious starch is more structured and elastic; its gel has a hardness of 3.5 N and maximum recovery strength.

Study of Structure and Phase Transformations in Rejuvenated Rapidly Quenched TiNiCu Alloys

Alloys of the quasibinary TiNi-TiCu system manufactured by melt quenching in the form of thin 20–50 μm ribbons have proven to show good potential as materials for the fabrication of micromechanical devices. At high cooling rates (about 106 K/s), this method allows producing high-copper (more than 20 at.%) amorphous alloys which exhibit an excellent shape-memory effect after crystallization. Their properties are known to largely depend on the crystallization conditions and the structure of the initial amorphous material acting as a precursor for the formation of crystal phases. It has been shown recently that the rejuvenation procedure (cryogenic thermocycling) of metallic glasses is one of the most promising methods of improving their properties. In this study, we investigated for the first time the effect of cryogenic thermocycling of rapidly quenched amorphous TiNiCu on the initial state, as well as on structure formation and the phase transformation patterns of subsequent crystallization conducted using various methods. The effect was analyzed utilizing the methods of scanning and transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry. The results show that rejuvenation treatment slightly reduces the glass transition and crystallization onset temperatures and moderately changes the sizes of structural features (grains, martensite plates), the quantity of the martensite phase, and the characteristic temperatures and enthalpy of the martensitic transformation.

Enhanced superconducting transition temperature for Cr-substituted Tl2Ba2CaCu2O8-δ

Cr-substituted Tl2Ba2CaCu2O8-δ (Tl-2212) high temperature superconductor for x = 0–0.5 has been prepared using the standard solid-state reaction method. The precursor powders consisting of Ba2CaCu2Od were sintered at 900 °C for 24 h. The powders were then added with Tl and Cr, ground and pressed into pellets. The pellets were heated at 910 °C in oxygen flow for 4 min followed by furnace cooling. The d.c. electrical resistance (R) versus temperature (T) measurements were carried out using the four-point probe method with silver paste contacts. The transition temperature was determined from the slope of the resistance versus temperature graph. The superconducting critical region was divided into three: onset transition temperature (Tc-onset), middle transition temperature (Tc-mid) and zero-resistance temperature (Tc-zero). The non-substituted sample showed onset transition temperature, Tc-onset of 97 K. The x = 0.2 sample (Tl1.8Cr0.2Ba2CaCu2O8-δ) showed the highest Tc-onset (102 K). Further substitutions of Cr (x ≥ 0.3) decreased the transition temperature. All samples except the non-substituted samples showed at least two peaks in the dR/dT curves. This indicated that superconductivity within grains and intergrain occurred at different temperatures for all Cr-substituted samples. This work showed that Cr (x = 0.2) slightly enhanced the transition temperature of Tl-2212.

Dragon fruit peel extract microcapsule incorporated pearl millet and dragon fruit pulp powder based functional pasta: formulation, characterization, and release kinetics study.

The pearl millet based functional pasta was formulated by incorporating freeze dried dragon fruit pulp powder and 2% (w/w) microcapsule containing dragon fruit peel extract. The control pasta consisted of 100% pearl millet flour. The other four functional pasta samples consisted of pearl millet and freeze-dried dragon fruit pulp powder (DFP) in the ratio of 95:5, 90:10, 85:15, and 80:20 (w/w), respectively. The inclusion of dragon fruit powder enhanced the swelling index, water absorption index, color, and functional properties of the pasta. The total phenolic content (0.24-0.43mg GAE/100g d.w.), antioxidant activity (17.76-30.67%), and betacyanin content (0.149-0.152mg/g d.w.) of the pasta was increased with the increase of dragon fruit pulp level in the formulation. The release kinetics of phenolic compounds into the simulated gastric juice was modeled using Higuchi and Peppas- Sahlin models. Out of these two models Peppas- Sahlin model ( and ) found to predict the release of phenolics into simulated gastric juice with respect to time of release when compared with Higuchi model ( and ). The onset of transition temperature and enthalpy of gelatinization of pasta samples was found to be in the range of 66.321-74.681°C and increased with the increase of dragon fruit level in the formulation.

AC Susceptibility and Electrical Properties of Ta-Substituted (TlTa)SrCaCuO Superconductor

The effects of Ta substitution on the superconducting properties of and (Tl1-xTax)Sr2CaCu2O7forx= 0.1 to 0.3 were reported. The characterization includes X-Ray diffraction, resistivity versus temperature measurement and AC susceptibility. All samples were prepared by the solid-state reaction method. The X-Ray diffraction pattern displayed the presence of Tl-1212 as the major phase for all samples. The resistance versus temperature curves for samplex= 0.3 showed onset transition temperature,Tconset and zero transition temperature,Tczero at 47 K and 30 K, respectively. AC susceptibility measurement showed susceptibility transition temperature,Tc χ’at 24 K and 30 K for samplex= 0.2 and 0.3, respectively. This study showed that higher substitution of Ta enhanced the superconducting properties of Tl-1212 superconductor.