Aircraft Observation and Simulation of the Supercooled Liquid Water Layer in a Warm Conveyor Belt over North China

This paper studied a snow event over North China on 21 February 2017,using aircraft in-situ data,a Lagrangian analysis tool,and WRF simulations with different microphysical schemes to investigate the supercooled layer of warm conveyor belts(WCBs).Based on the aircraft data,we found a fine vertical structure within clouds in the WCB and highlighted a 1-2 km thin supercooled liquid water layer with a maximum Liquid Water Content(LWC) exceeding0.5 g kg^(-1) during the vertical aircraft observation.Although the main features of thermodynamic profiles were essentially captured by both modeling schemes,the microphysical quantities exhibited large diversity with different microphysics schemes.The conventional Morrison two-moment scheme showed remarkable agreement with in-situ observations,both in terms of the thermodynamic structure and the supercooled liquid water layer.However,the microphysical structure of the WCB clouds,in terms of LWC and IWC,was not apparent in HUJI fast bin scheme.To reduce such uncertainty,future work may focus on improving the representation of microphysics in bin schemes with in-situ data and using similar assumptions for all schemes to isolate the impact of physics.

Investigation of Micro Formability of Bulk Amorphous Alloy in the Supercooled Liquid State Based on Fluid Flow and Finite Element Analysis

Research results on the viscous flow deformation behavior of bulk amorphous alloy in different systems are reviewed. The material exhibits an ideal Newtonian fluid at a high temperature. Analytical solution of lamellar fluid flow behavior is used to discuss the viscous flow behavior of the bulk amorphous alloy in the supercooled liquid state. A material model, which describes such deformation behavior of Mg6oCusoYlo amorphous alloy, is introduced into the finite element method of microformin8 process. Surface feature size was investigated and found not sensitive to the micro formability. Bulk amorphous alloy may possibly be applied to microelectro-mechanical-systems （MEMS） fabrication.

VARIATIONAL CALCULATION OF THERMODYNAMIC PROPERTIES OF SUPERCOOLED LIQUID METALS

By means of Gibbs-Bogoliubov (GB) thermodynamic variational calculation,the thermodynamic properties of the supercooled liquid metals,such as the 3rd family elements Al,Ga and Tl and transition metal Ti were calculated using the hard-sphere (HS) system as reference.The values of mean atomic volume,Helmholtz free energy,internal energy and entropy as well as specific heat at constant volume,isothermal bulk modulus,thermal expan- sion coefficient and specfic heat under constant pressure were evaluated.The glass transition temperature,T_g,is easily obtained from the C_p-T plot.The glass forming ability for metal can be predicted from T_g/T_m,which is in agreement with the experimental results.

Direct measurement of the surface dynamics of supercooled liquid-glycerol by optical scanning a film

The surface dynamics of supercooled liquid-glycerol is studied by scanning the thickness of the glycerol film with single photon detection. Measurements are performed at room temperature well above the glyeerol＇s glass transition temperature. It is shown that the surface dynamics of the glycerol film is very sensitive to the temperature. The linear relationship between the thickness of the film and the viscosity predicted by the Vogel Pulcher-Tammann Hesse （VFTH） law is also presented experimentally.

Jamming in confined geometry:Criticality of the jamming transition and implications of structural relaxation in confined supercooled liquids

In marginally jammed solids confined by walls,we calculate the particle and ensemble averaged value of an order parameter,Ψ(r),as a function of the distance to the wall,r.Being a microscopic indicator of structural disorder and particle mobility in solids,Ψis by definition the response of the mean square particle displacement to the increase of temperature in the harmonic approximation and can be directly calculated from the normal modes of vibration of the zerotemperature solids.We find that,in confined jammed solids,Ψ(r)curves at different pressures can collapse onto the same master curve following a scaling function,indicating the criticality of the jamming transition.The scaling collapse suggests a diverging length scale and marginal instability at the jamming transition,which should be accessible to sophisticatedly designed experiments.Moreover,Ψ(r)is found to be significantly suppressed when approaching the wall and anisotropic in directions perpendicular and parallel to the wall.This finding can be applied to understand the r-dependence and anisotropy of the structural relaxation in confined supercooled liquids,providing another example of understanding or predicting behaviors of supercooled liquids from the perspective of the zero-temperature amorphous solids.

Influence of Rolling Temperature in Supercooled Liquid Region on the Surface Morphology of Zr_(52.5)Al_(10)Ni_(10)Cu_(15)Be_(12.5) Bulk Metallic Glass

Surface morphologies of Zr52.5 Al10 Ni10 Cu15 Be12.5 bulk metallic glass after being rolled at both a temperature around T9 and near （ Tx - 50） K were investigated with a scanning electron microscopy. Macroscopic and microscopic observation results show that squamae, cracks, steps and wedges exist on the surface when the samples were rolled at temperatures around Ty. However, a smooth and fiat surface appears when the samples were rolled at temperatures near （ Tx - 50） K. These results indicate that the mode of deformation in the supercooled liquid region is a partially homogeneous flow at a temperature around T9, and a fully homogeneous one at temperatures near （ Tx - 50） K. According to the results, it is more feasible to roll the amorphous alloys at temperatures near （ Tx - 50） K to obtain parts with smooth and fiat surface.

LOCAL STRUCTURE OF SUPERCOOLED LIQUID Ni80P20 ALLOY

Local arrangement of atoms in supercooled liquid Ni_(80)P_(20) alloy has been investigated by using NPT-MD simulation techniques based on the effective pair Potentials derived for Ni-P system. Bond-orientational order, the long-range correlation function and symmetrical parameters by pair-analysis approach have been calculated for supercooled liquid Ni_(80)P_(20) alloy. Results show. that in case of Ni_(80) .P_(20) alloy, the local structure is all random-like whether the centre of cluster is located at atoms Ni or P. It indicates that the icosahedral symmetry is not the unique model to describe the microstructure in supercooled liquid metals.

Unveiling the time-temperature dependence of metastability of supercooled liquid using nano-calorimetry

There is a lack of understanding of both the conversion of an unstable glass into a metastable supercooled liquid(MSL) upon heating and the metastability of MSLs. In this study, we investigated the time-and temperature-dependent metastability of an MSL using an advanced nano-calorimetric technique. The chosen Au-based metallic glass(Au MG) allowed adequate probing of its MSL in a temperature range between 10 and 70 K above the standard glass transition temperature. We found that the survival time of the MSL state is a quadratic function of temperature. Beyond this duration threshold, the sample undergoes fast crystallization even if it is below the crystallization temperature that is measured using differential scanning calorimetry.Employing transmission electron microscopy, we observed the formation of clusters with a partially ordered lattice structure during relaxation in the Au MG sample fabricated using a nano-calorimeter. The atomic ordering within the clusters was enhanced by increasing time and temperature in the MSL region. Once the as-produced glass entered the MSL stage upon heating followed by a quenching stage at a given rate, the mechanical properties of the quenched glass remained the same regardless of its holding temperature and duration within the MSL region. This work provides insights into the glass-MSL-crystal transformation and offers guidance for designing standard metallic glasses for property characterizations.

Tailoring the mechanical properties of bulk metallic glasses via cooling from the supercooled liquid region

Structural rejuvenation is vital and attractive for modulating the energetic state and structural heterogeneity of bulk metallic glasses(BMGs). In this paper, we show that cooling a BMG from a supercooled liquid region at laboratory rates can reverse the relaxation enthalpy lost during the preceding structural relaxation. Increasing the cooling rate is beneficial for enhancing atomic mobility and dynamic mechanical relaxation intensity. Therefore, this rejuvenation methodology promotes tailoring the mechanical properties of BMGs and provides a comprehensive understanding of the rejuvenation mechanism.

Entropy-driven atomic activation in supercooled liquids and its link to the fragile-to-strong transition

As a common but critical dynamic crossover in glass-forming liquids(GFLs),the discovery of fragile-to-strong(F-S)transition promises a novel route for understanding supercooled liquid and glass transition.The present work,for the first time,successfully realizes the quantitative prediction of the F-S transition in nine metallic glass-forming liquids,by a counter-intuitive approach that focuses on local atomic activation events,rather than relaxation,upon cooling.The dynamic crossover originates from a disorder-to-order transition by self-regulating behavior of atomic position within a cage controlled by finite atomic activation events,due to the appearance of local cooperative motion of nearest neighborhood atoms.Moreover,the dominant role of entropy in this anomaly has been discovered,and the correspondence between the crossover of configuration entropy involved in activation events and the occurrence of F-S transition has been found.Our work implies that the feature of atomic energy fluctuations reflected by atomic activation events has a close linkage to complex dynamic behaviors of disordered systems.

Identifying Supercooled Liquid Water in Cloud Based on Airborne Observations: Correlation of Cloud Particle Number Concentration with Icing Probability and Proportion of Spherical Particles

Identifying supercooled liquid water(SLW)in clouds is critical for weather modification,aviation safety,and atmospheric radiation calculations.Currently,aircraft identification in the SLW area mostly depends on emprical estimation of cloud particle number concentration(N_(c))in China,and scientific verification and quantitative identification criteria are urgently needed.In this study,the observations are from the Fast Cloud Droplets Probe,Rosemount ice detector(RICE),and Cloud Particle Imager(CP_(i))onboard a King Air aircraft during seven flights in 2018 and 2019 over central and eastern China.Based on this,the correlation among N_(c),the proportion of spherical particles(P_(s)),and the probability of icing(P_(i))in supercooled stratiform and cumulus-stratus clouds is statistically analyzed.Subsequently,this study proposes a method to identify SLW areas using N_(c) in combination with ambient temperature.The reliability of this method is evaluated through the true skill statistics(TSS)and threat score(TS)methods.Numerous airborne observations during the seven flights reveal a strong correlation among Nc,P_(s),and P_(i)at the temperature from 0 to−18°C.When Nc is greater than a certain threshold of 5 cm^(−3),there is always the SLW,i.e.,P_(i)and P_(s)are high.Evaluation results demonstrate that the TSS and TS values for Nc=5 cm^(−3)are higher than those for Nc<5 cm^(−3),and a larger Nc threshold(>5 cm^(−3))corresponds to a higher SLW identification hit rate and a higher SLW content.Therefore,Nc=5 cm^(−3)can be used as the minimum criterion for identifying the SLW in clouds at temperature lower than 0°C.The SLW identification method proposed in this study is especially helpful in common situations where aircraft are equipped with only Nc probes and without the CP_(i)and RICE.

Dissociation behavior of “dry water” C_3H_8 hydrate below ice point:Effect of phase state of unreacted residual water on a mechanism of gas hydrates dissociation

The results on a dissociation behavior of propane hydrates prepared from ＂dry water＂ and contained unreacted residual water in the form of ice inclusions or supercooled liquid water（water solution of gas） were presented for temperatures below 273 K.The temperature ramping or pressure release method was used for the dissociation of propane hydrate samples.It was found that the mechanism of gas hydrate dissociation at temperatures below 273 K depended on the phase state of unreacted water in the hydrate sample.Gas hydrates dissociated into ice and gas if the ice inclusions were in the hydrate sample.The samples of propane hydrates with inclusions of unreacted supercooled water only（without ice inclusions） dissociated into supercooled water and gas below the pressure of the supercooled water-hydrate-gas metastable equilibrium.

Influence of flux treatment on the glass forming ability of Pd-Si binary alloys

Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.

Unraveling the morphological evolution mechanism of solid sulfur species in lithium-sulfur batteries with operando light microscopy

Solid-liquid phase conversion between various sulfur species in lithium-sulfur(Li-S)batteries is a fundamental reaction of the sulfur cathode.Disclosing the morphological evolution of solid sulfur species upon cycling is of great significance to achieving high energy densities.However,an in-depth investigation of the internal reaction is still lacking.In this work,the evolution process of solid sulfur species on carbon substrates is systematically studied by using an operando light microscope combined with in situ electrochemical impedance spectra technology.The observation of phenomena such as bulk solid sulfur species can form and dissolve independently of the conductive substrates and the transformation of supercooled liquid sulfur to crystalline sulfur.Based on the phenomena mentioned above,a possible mechanism was proposed in which the dissolution reaction of solid sulfur species is a spatially free reaction that involves isotropic physical dissolution,diffusion of molecules,and finally the electrochemical reaction.Correspondingly,the formation of solid sulfur species tends to be a form of crystallization in a saturated solution rather than electrodeposition,as is commonly believed.Our findings offer new insights into the reaction of sulfur cathodes and provide new opportunities to design advanced sulfur cathodes for Li-S batteries.

Gibbs Free Energy and Activation Energy of ZrTiAlNiCuSn Bulk Glass Forming Alloys

The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr_(52.5)Ti_5Al_(10)-Ni_(14.6)Cu_(17.9))_((100-x)/100)Sn_x (x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equationproposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease firstas the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Snlarger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by adecrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9) and(Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9))_(0.97)Sn_3 was evaluated by Kissinger equation. It is noted that the Sn addition increases theactivation energies for glass transition and crystallization, implying that the higher thermal stability can be obtainedby appropriate addition of Sn.

Synthesis,properties and XPS analysis of Cu-,Ni-,Ti-based metallic glasses

Metallic glasses(MG)represent an interesting group of materials as they possess outstanding physical,chemical and mechanical properties compared to their crystalline counterparts.This paper reviews the synergistic influence of Ni and Nb elements on thermal stability of supercooled liquid and corrosion resistance of as-cast Cu-Zr(Hf)-Ti-Ni-Nb bulk metallic glasses(BMGs).Additionally,in-situ second phase reinforced Cu-based BMG composites with high corrosion resistance and excellent mechanical properties are investigated.On the other hand,this paper reports the development of ultra-high corrosion resistant Ni-based metallic glasses at high temperatures for their potential applications.Corrosion resistance and XPS analysis of the Nifree Ti-based BMG are also introduced.

Constraint Cooling of Hot Rolled Coil

Amorphous ribbons of Fe 74Al 4Sn 2(PSiB) 20 alloy have been synthesized by melt spinning and axial design method. The thermal properties of the amorphous ribbons have been measured by differential scanning calorimeter (DSC). The DSC results show that the Fe 74Al 4Sn 2P 12Si 4B 4 amorphous alloy has relatively wider supercooled liquid region with a temperature interval of 40 38 K (ΔT x=T x-T g). The alloys with a higher phosphorous content in the metalloid element composition triangle of Fe 74Al 4Sn 2(PSiB) 20 have high glass forming ability. The amorphous alloys also show good magnetic properties in which Fe 74Al 4Sn 2P 6 67Si 6 67B 6 67 alloy has a large maximum permeability (μ m), Fe 78Al 4Sn 2P 3Si 3B 10 alloy exhibits a high square ratio (B r/B 10) and Fe 74Al 4Sn 2P 4Si 12B 4 shows a low core loss (P 0 5/1 3T). High glass forming ability and good magnetic properties make Fe 74Al 4Sn 2(PSiB) 20 amorphous alloys valuable in future research.

Crystallization of Pd_40Cu_30Ni_10P_20 bulk metallic glass with and without pressure

The glass-transition behavior of Pd40Cu30Ni10P20 bulk metallic glass was investigated by differential scanning calorimetry （DSC） and X-ray powder diffraction （XRD）. The effect of pressure on the crystallization behavior of Pd40Cu30Ni10P20 bulk glass was studied by in situ high-pressure and high-temperature X-ray powder diffraction using synchrotron radiation. Phase analyses show at least six crystalline phases in the crystallized sample, namely, monoclinic, tetragonal CuaPd-like, rhombohedral, fcc-Ni2Pd2P, fcc-（Ni, Pd） solid solution, and body-centered tetragonal （bct） NiaP-like phases. The onset crystallization temperature increases with pressure having a slope of 1 1 K/GPa in the range of 0 to 4 GPa. The results are attributed to the competing process between the thermodynamic potential barrier and the diffusion activation energy under pressure.

Shear-accelerated crystallization of glass-forming metallic liquids in high-pressure die casting

As one of the most important forming technologies for industrial bulk metallic glass (BMG) parts withcomplex shapes, high-pressure die casting (HPDC) can fill a die cavity with a glass-forming metallic liquidin milliseconds. However, to our knowledge, the correlation between flow and crystallization behavior inthe HPDC process has never been established. In this study, we report on the solidification behavior ofZr_(55)Cu_(30)Ni_(5)Al_(10) glass forming liquid under various flow rates. Surprisingly, the resulting alloys display adecreasing content of amorphous phase with increase of flow rate, i.e. increase of cooling rate, suggestingthat crystallization kinetics of glass-forming metallic liquids in the HPDC process is strongly dependenton the flow field. Analysis reveals that the accelerated crystallization behavior is mainly ascribed to therapid increase in viscosity with a decreasing temperature as well as to the huge shear effect in the glassforming liquid at the end stage of the filling process when the temperature is close to the glass-transitionpoint;this results in a transition from diffusion- to advection-dominated transport. The current investigation suggests that flow-related crystallization must be considered to assess the intrinsic glass-formingability of BMGs produced via HPDC. The obtained results will not only improve the understanding ofcrystallization dynamics but also promote the high-quality production and large-scale application of BMGparts.

Thermoplastic micro-formability of TiZrHfNiCuBe high entropy metallic glass

High entropy metallic glasses（MGs） have attracted tremendous attentions owing to high entropy that benefits the probing of new MG-forming systems. However, the micro-formability of high entropy MGs is lack of investigation in comparison with these conventional MG counterparts, which is crucial to the development of this kind of metallic alloys. In this work, the thermoplastic mciro-formability of TiZrHfNiCuBe high entropy MG was systemically investigated. Time-Temperature-Transformation（TTT）curve was first constructed based on isothermal crystallization experiments, which provides thermoplastic processing time of the supercooled high entropy MGs. By comparison with the deformation map,Newtonian flow was found beneficial to the thermoplastic formability. While the thermoplastic forming becomes arduous with reducing mould size to tens micrometer, because of the strong supercooled TiZrHfNiCuBe high entropy MG（fragility = 27）. Fortunately, the micro-formability of TiZrHfNiCuBe high entropy MG could be improved by vibration loading, as demonstrated by finite-element-method simulation. Our findings not only systemically evaluate the thermoplastic micro-formability of high entropy MG, but also provide fundamental understanding of the phenomenon.