Crystallization kinetics of phase change materials (PCMs) at high temperatures is of key importance for the extreme speed of data writing and erasing. In this work, the crystallization behavior of ...one of the typical PCMs, GeTe, has been studied using ultrafast differential scanning calorimetry (DSC) at high heating rates up to 4 × 104 K s–1. A strong non-Arrhenius temperature-dependent viscosity has been observed. We considered two viscosity models for estimating the crystal growth kinetics coefficient (U kin). The results showed that the MYEGA model was more suitable to describe the temperature-dependent viscosity and the crystal growth kinetics for supercooled liquid GeTe. The glass transition temperature (T g) and fragility m were estimated to be 432.1 K and 130.7, respectively. The temperature-dependent crystal growth rates, which were extrapolated by the MYEGA model, were in line with the experimental results that were measured by in situ transmission electron microscopy at a given temperature. The crystal growth rate reached a maximum of 3.5 m s–1 at 790 K. These results based on ultrafast DSC with the MYEGA model offer a revelation for crystallization kinetics of supercooled liquid GeTe.
The kinetic behaviors and magnetocaloric properties of LE, ME, and HE MGs.
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•(GdTbDy)CoAl metallic glasses (MGs) with low-, medium-, and high-entropy (HE) and critical diameters of ...more than 5 mm were fabricated.•The high configuration entropy could promote atomic motion, leading to the reduction of viscosity and deterioration of glass-forming ability.•The notable ordered structure in HE MGs slightly decreases activation energies for glass transition and crystal growth.•The high structural order, spin glass behaviors, and complicated compositions comprehensively contribute to outstanding magnetocaloric effects.
The effect of configuration entropy (ΔSconf) on thermal properties and magnetocaloric effects (MCE) of metallic glasses (MGs) remains vague. In this work, Tb55Co17.5Al27.5 low-, (Gd0.5Tb0.5)55Co17.5Al27.5 medium-, and (Gd1/3Tb1/3Dy1/3)55Co17.5Al27.5 high-entropy (LE, ME, and HE) MGs with critical diameters more than 5 mm were successfully fabricated. Systematic investigations into their thermodynamic behaviors suggest that high ΔSconf might deteriorate glass forming ability (GFA) along with reduced viscosity. Simultaneously, an improved thermal stability was observed in ME and HE MGs for their high activation energies for glass transition, crystal nucleation and growth, while the notable ordered structure in HE MG could accelerate glass transition and crystal growth by reducing activation energies. Studies of MCE indicate that the distinguished spin glass behaviors and higher structural order in HE MGs comprehensively contribute to an enhanced relative cooling power and a broader magnetic-transition temperature range, whereas the change of Curie temperature and maximum magnetic entropy more depends on the de Gennes factor rather than ΔSconf. All three designed MGs manifesting the competitive GFA and MCE could be candidates for magnetic refrigeration. Our studies show that entropy tailoring seems to play a dominant role in determining thermodynamic behaviors, which could help to design more stable MCE MGs.
In this article, we report the formation of the high-entropy Gd20Tb20Dy20Al20M20 (M = Fe, Co and Ni) bulk metallic glasses with good magnetocaloric properties. Compared with most of the rare earth ...based metallic glasses, these alloys are found to have the comparably large maximum magnetic entropy changes (ΔSM), but much broader widths of the ΔSM peaks, and hence larger refrigerant capacity (RC). This can be attributed to the combination of the spin glass behaviors and the complicated compositions in these alloys. Our work show that the high entropy bulk metallic glasses is a promising candidate material as the magnetic refrigerant.
•The high-entropy bulk metallic glasses with good MCE were fabricated.•The HE-BMGs show large maximum magnetic entropy changes.•The spin glass behavior makes the magnetic entropy change peaks much broader.•Their magnetic transition temperature can be tuned in a large temperature range.
Fine particulate matter (PM2.5) has recently been associated with the activation of the hypothalamus–pituitary–adrenal (HPA) axis, increasing cardiometabolic risks. However, it is unknown which ...constituents of PM2.5 were mainly responsible for these associations. In a longitudinal panel study with 4 repeated measurements among 43 college students in Shanghai, China, we measured serum levels of corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol, as indicators of HPA axis activation. Then, we evaluated the associations of 22 constituents of PM2.5 with these stress hormones using linear mixed-effect models. During the study period, the average daily concentration of PM2.5 was 41.1 μg/m3. We found that short-term exposure to PM2.5 was associated with elevated levels of the 3 stress hormones. We observed that water-soluble inorganic ions, especially nitrate (NO3−) and ammonium, had stronger influences on 3 hormones. Six metallic elements, including Zn, Mn, Cu, Fe, Br, and Cr, had positive but generally instable associations with 3 hormones. The effects of organic carbon and elemental carbon on hormones were generally weak. When correcting for multiple comparisons using false discovery rate, NO3− was still significantly associated with CRH, but other important associations turned to be insignificant. An interquartile range increase in NO3− on the previous day were associated with 12.13% increase (95% confidence interval: 4.45%, 20.37%) in CRH. Our findings suggested that water-soluble inorganic constituents of PM2.5 (especially, NO3−) might have stronger influences on the activation of HPA axis than carbonaceous and elemental components.
•PM2.5 may activate the HPA axis by increasing the secretion of stress hormones.•PM2.5 was associated with CRH and ACTH at lag 1 d and with cortisol at lag 2 d.•NO3− might have stronger influence on the HPA axis activation.•OC, EC and metals in PM2.5 might have weak and instable impacts on the HPA axis.
Systemic inflammation is considered one of the key mechanisms in the development of cardiovascular diseases induced by fine particulate matter (PM2.5) air pollution. However, evidence concerning the ...effects of various PM2.5 constituents on circulating inflammatory biomarkers were limited and inconsistent.
To evaluate the associations of short-term exposure to a variety of PM2.5 constituents with circulating inflammatory biomarkers.
We conducted a panel study from May to October 2016 among 40 healthy adults in Shanghai, China. We monitored the concentrations of 27 constituents of PM2.5. We applied linear mixed-effect models to analyze the associations of PM2.5 and its constituents with 7 inflammatory biomarkers, and further assessed the robustness of the associations by fitting models adjusting for PM2.5 mass and/or their collinearity. Benjamini-Hochberg false discovery rate was used to correct for multiple comparisons.
The associations of PM2.5 were strongest at lag 0 d with tumor necrosis factor-α (TNF-α), at lag 1 d with interleukin-6, interleukin-8, and interleukin-17A, at lag 02 d with monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1 (ICAM-1). After correcting for multiple comparisons in all models, Cl−, K+, Si, K, As, and Pb were significantly associated with interleukin-8; SO42− and Se were marginally significantly associated with interleukin-8; SO42−, As, and Se were marginally significantly associated with TNF-α; and Si, K, Zn, As, Se, and Pb were marginally significantly associated with MCP-1.
Our results suggested that some constituents (SO42−, Cl−, K+, and some elements) might be mainly responsible for systemic inflammation triggered by short-term PM2.5 exposure.
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•It remains unclear how PM2.5 constituents affect systemic inflammation differently.•27 constituents and 7 inflammatory biomarkers were evaluated in Shanghai, China.•SO42−, Cl−, K+ and some elements may be responsible for inflammation.
An electrode with low performance or limited endurance for water splitting hydrogen generation has been the key limitation for application of hydrogen in contemporary clean-energy technologies. In ...this paper, an Al
80
Ni
6
Co
3
Mn
3
Y
5
Au
3
metallic glass ribbon with outstanding catalytic activity in the hydrogen evolution reaction (HER) in acidic solutions is fabricated for the first time. Its overpotential is about 70 mV @ 10 mA cm
−2
and Tafel slope is about 39 mV dec
−1
, which are comparable to those of commercial noble Pt/C electrodes (33 mV @ 10 mA cm
−2
and 38 mV dec
−1
). Such a high catalytic reactivity is attributed to the synergic effect of multiple elements that disperse atomically homogeneously on the nanoporous surface. The outstanding catalytic activity persists and even becomes much better over a long-time reaction, which is attributed to the formation of a protective Au-rich layer in the interface. The Al-based metallic glass ribbon is flexible with high yield strength, large elasticity and good electrical conductivity, which are desirable and promising characteristics for a free-standing catalytic electrode in the HER.
Al-based metallic glass ribbon with a nanoporous layer of high-entropy alloy is a robust advanced self-stabilized free-standing electrode for hydrogen evolution reaction.
Multicomponent alloys are promising candidates as catalysts for hydrogen evolution reaction (HER) in aqueous solutions owing to the synergic effects between elements. However, due to the vast ...compositional space they occupy, identifying the optimum catalyst is challenging both computationally and experimentally. In this paper, we propose a scalable high-throughput bubble screening method that is able to identify the multicomponent alloys with the highest catalytic properties. As a demonstration, the optimum compositions with advanced intrinsic catalytic activities in the ternary Ni–Co–Ti and Ni–Fe–Au alloys are identified using this method. The advanced catalytic performance of the optimum Ni56.5Co35Ti8.5 alloy ribbon is further confirmed by the individual electrochemical tests, with an over-potential of about 425 mV at 500 mA cm–2 and a Tafel slope of about 82 mV dec–1. This is attributed to the low atomic packing density and low electron binding energy. The introduced scalable high-throughput strategy is not limited to ternary catalysts for HER but is also expected to be equally useful for exploring catalysts in higher composition alloy systems and even for oxygen evolution reactions.
Isothermal annealing is a very useful strategy in modulating the properties and structures of metallic glasses, which has been regarded as a single relaxation progress. In this work, the enthalpy ...relaxation of Au-based metallic glasses are studied using a high-precision calorimetry. An intriguing transition from β relaxation to α relaxation was confirmed during isothermal annealing. Energy landscape model is proposed to quantitatively explain how the relaxation modes transform. It is found that a small enthalpy decrease (about 0.8 kJ/mol) in initial state causes an extremely large increase (about 100 kJ/mol) in relaxation barrier, which is attributed to the enhanced cooperative atomic motion. These results open a gate for precisely understanding the role of different relaxation modes in modifying the properties of metallic glasses.
•Relaxation kinetics of metallic glasses during isothermal annealing is studied.•Intriguing transition from β relaxation to α relaxation is confirmed.•A small enthalpy decrease in initial state can cause an extremely large increase in relaxation barriers.
The identification of constituents of fine particulate matter (PM2.5) air pollution that had key impacts of ischemic stroke (the predominant subtype of stroke) is important to understand the ...underlying biological mechanisms and develop air pollution control policies.
To explore the associations between PM2.5 constituents and hospitalization for ischemic stroke in Shanghai, China.
We conducted a time-series study to explore the associations between 27 constituents of PM2.5 and hospitalization for ischemic stroke in Shanghai, China from 2014 to 2016. The over-dispersed generalized additive models with adjustment for time, day of week, holidays, and weather conditions were used to estimate the associations. We also evaluated the robustness of the effect estimates for each constituent after adjusting for the confounding effects of PM2.5 total mass and gaseous pollutants and the collinearity (the residual) between this constituent and PM2.5 total mass. We also compared the associations between seasons.
In total, we identified 4186 ischemic stroke hospitalizations during the study period. The associations of ischemic stroke were consistently significant with elemental carbon and several elemental constituents (Chromium, Iron, Copper, Zinc, Arsenic, Selenium, and Lead) at lag 1 day in single-constituent models, models adjusting for PM2.5 total mass or gaseous pollutants and models adjusting for collinearity. The associations were much stronger in cool season than in warm season.
The current study provides suggestive evidence that elemental carbon and some metallic elements may be mainly responsible for the risks of ischemic stroke hospitalization induced by short-term PM2.5 exposure.
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•Few evidence on the associations between PM2.5 constituents and ischemic stroke•The effects of PM2.5 on ischemic stroke hospitalizations varied by constituents.•Elemental carbon and some trace elements might be mainly responsible.
To reduce air pollution within a 300 km radius from Hangzhou (the capital city of Zhejiang Province in East China) for the 2016 G20 summit (9/4–9/5), the 14-day (8/24–9/6) stringent pollution control ...measures were implemented in Shanghai. Changes in atmospheric concentrations during the same 14-day period from 2014 to 2016 were examined at two Supersites, i.e., urban Pudong site (PD) and Dianshan Lake regional site (DSL). Up to 50% reductions were found for PM2.5, with 13.1% and 9.7% reductions for SO2 and NO2, respectively. No apparent improvements were found for 8-h average O3 concentrations. Large reductions were also found for SO42− (51.4%), NO3− (68.8%), and NH4+ (84.4%), on average. Elevated coefficient of divergence values (0.52–0.56) suggested that pollutant sources differed at the two sites. Biomass burning, resuspended dust, combustion, iron and steel industry, sea salt, secondary aerosol, and vehicle exhaust were identified at the DSL site by Positive Matrix Factorization (PMF). Secondary aerosol and vehicle exhaust accounted for 45.7% of PM2.5 mass, followed 11.2%–13.7% each by industry, resuspended dust, and coal and oil combustion.
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•Effectiveness of the pollution control measures was evaluated for the G20 summit.•Concentrations of most of criteria air pollutants reduced whereas O3 elevated.•Impacts of local emissions and regional transport were analyzed at two Supersites.•Secondary aerosols and vehicle exhaust remained the top two sources of PM2.5.
