Investigation of Thermophysical Properties of Zr-Based Metallic Glass-Polymer Composite

Composites based on Zr65Cu17.5Ni10Al7.5 metallic glass (MG) and polytetrafluoroethylene (PTFE) were prepared by ball milling. Different composites (30/70, 50/50 and 70/30) were produced. Samples for dynamic mechanical analysis and laser flash analysis were fabricated in the supercooled region of the metallic glass and viscous region of the polymer. Spark plasma sintering (SPS) was performed at the supercooled region for the metallic glass powder. Characteristics such as thermal, mechanical, and structural properties were studied. A formation of the Zr2Cu and Zr2Ni intermetallic was found in the metallic glass after SPS. A formation of the nanocrystalline Zr2Cu was found in composite samples. Dynamical mechanical analysis (DMA) was used to study the mechanical behavior of the material. It was concluded that the 70/30-MG/PTFE composite sample had better thermal conductivity than the other composite samples. The thermal conductivity of the metallic glass was the highest among the samples and it increased with the MG content in composites.

The Water Polymorphism and the Liquid–Liquid Transition from Transport Data

NMR spectroscopic literature data are used, in a wide temperature-pressure range (180–350 K and 0.1–400 MPa), to study the water polymorphism and the validity of the liquid–liquid transition (LLT) hypothesis. We have considered the self-diffusion coefficient DS and the reorientational correlation time τθ (obtained from spin-lattice T1 relaxation times), measured, respectively, in bulk and emulsion liquid water from the stable to well inside the metastable supercooled region. As an effect of the hydrogen bond (HB) networking, the isobars of both these transport functions evolve with T by changing by several orders of magnitude, whereas their pressure dependence become more and more pronounced at lower temperatures. Both these transport functions were then studied according to the Adam–Gibbs model, typical of glass forming liquids, obtaining the water configurational entropy and the corresponding specific heat contribution. The comparison of the evaluated CP,conf isobars with the experimentally measured water specific heat reveals the full consistency of this analysis. In particular, the observed CP,conf maxima and its diverging behaviors clearly reveals the presence of the LLT and with a reasonable approximation the liquid–liquid critical point (LLCP) locus in the phase diagram.

Molecular dynamics study of wetting of alkanes on water: From high temperature to the supercooled region and the influence of second inflection points of interfacial tensions

To explore the wetting behavior of alkanes on bulk water interfaces, molecular dynamics simulations were carried out to determine the temperature dependence of (1) the surface tension of alkanes (octane,...

A computational study of Stillinger–Weber silicon at 0.75 GPa in supercooled region

We studied the liquid-liquid transition in supercooled silicon modeled by the Stillinger–Weber potential. The Isothermal Isobaric Monte Carlo (NPT-MC) simulation techniques were performed here to compute the free energy difference between the two liquid phases of silicon by Bennett Acceptance Ratio (BAR) method along with a reversible path at 0.75 GPa pressure and 970 K temperature. The thermodynamic properties as energy ([Formula: see text]) and density ([Formula: see text]) of the high-density liquid (HDL) phase have been computed here at different temperatures from 970–990 K. We also computed the entropy difference between the high-density liquid (HDL) and low-density liquid (LDL) phases which indicates that the glass transition temperature for the LDL phase is lower compared to the HDL phase. Further, by using the BAR method, we have computed the excess Gibbs free energy (G[Formula: see text]) of HDL phase with respect to the crystalline phase at different temperatures in the supercooled region of SW-Silicon potential model. Based on the slope of excess Gibbs free energy with respect to temperature (T), we found that the excess entropy (Se) of the HDL with respect to crystalline phase shows a nonmonotonic dependence on temperature at the liquid-liquid transition temperature of T[Formula: see text] = 970 K. Our results are in good agreement with the previous observation of a nonmonotonic dependence of the enthalpy on temperature in MD simulations, starting with the HDL phase at a temperature just above T[Formula: see text]. All these properties are useful to understand the phase behavior of supercooled silicon and can be applicable to identify the better quality of silicon for industrial uses.

Experimental (FTIR, BDS) and theoretical analysis of mutarotation kinetics of d-fructose mixed with different alcohols in the supercooled region

The mutarotation kinetics of pure molten d-fructose and its binary mixture with alcohols (i.e., sorbitol and maltitol) have been reported using Fourier transform infrared, broadband dielectric spectroscopy and density functional theory calculations.

Multiscale approach for studying melting transitions in CuPt nanoparticles

Melting temperature dependence on the radius of CuPt clusters by CALPHAD and atomistic molecular dynamics simulations. The formation of a supercooled region for 3 nm particle is highlighted by the huge hysteresis during the freezing process.