Study on the Thermo Physical Properties of Deeply Undercooled Silver Melts

2014 ◽  
Vol 1081 ◽  
pp. 332-337
Author(s):  
Li Xin Li ◽  
Jun Liang Zhao ◽  
Guo Hua Cao ◽  
Xue Mao Guan
Keyword(s):  
Specific Heat ◽  
Solid Phase ◽  
Entropy Change ◽  
Energy Difference ◽  
Processing Technique ◽  
Pure Silver ◽  
Gibbs Free Energy Difference ◽  
Equilibrium Solidification ◽  
Undercooled Melt ◽  
Measured Specific Heat

Using the flux processing technique, the undercooling of pure silver melts could reach to 205K. Combining the Differential Scanning Calorimeter (DSC) technique, the specific heat of pure silver melts was measured, which showed a linear dependence on temperature in the range of the obtained undercooling from 0 K to 205K. The related thermodynamic properties of silver, such as the entropy change, the enthalpy change and the Gibbs free energy difference between the undercooled melt and the solid phase, were derived from the measured specific heat. The results showed that the model of Singh-Holz can reveal the reality of the non-equilibrium solidification more accurately than other models.

Melting vs. Solidification of a Pure Metal Analysed by DSC

1997 ◽  
Vol 481 ◽  
Author(s):  
N. Clavaguera ◽  
M. T. Clavaguera-Mora ◽  
J. Fontán ◽  
J. L. Touron ◽  
C. Comas
Keyword(s):  
Energy Difference ◽  
Pure Metal ◽  
Continuous Heating ◽  
Isothermal Hold ◽  
Equilibrium Conditions ◽  
Equilibrium Melting Temperature ◽  
Gibbs Free Energy Difference ◽  
Undercooled Melt ◽  
Isothermal Regime ◽  
Non Equilibrium

ABSTRACTThe aim of the present paper is to analyse the melting/solidification of pure metals resulting from non-equilibrium conditions. Attention is focused on the direct measurement of the calorimetric signal obtained under isothermal hold of the sample at a temperature close to the equilibrium melting temperature Tm, which results in both melting of an overheated solid and solidification of an undercooled melt. The non-equilibrium transformations are monitored by DSC under isothermal regime, with previous continuous heating/continuous cooling of the sample. The dependence of the calorimetric signal on thermodynamic factors, ΔH and ΔG, is explored. Here ΔH and ΔG are, respectively, the melting enthalpy and Gibbs free energy difference between the crystal and the liquid. In particular, the results of the investigation performed on the melting/solidification behaviour of pure In and Pb are presented.

The specific heats of three paramagnetic salts at very low temperatures

1956 ◽  
Vol 237 (1210) ◽  
pp. 395-403 ◽  
Keyword(s):  
Specific Heat ◽  
Absolute Temperature ◽  
Magnesium Nitrate ◽  
Paramagnetic Resonance ◽  
Specific Heats ◽  
Ammonium Alum ◽  
Relaxation Measurements ◽  
Ferric Ammonium ◽  
The Absolute ◽  
Measured Specific Heat

The specific heats of three paramagnetic salts, neodymium magnesium nitrate, manganous ammonium sulphate and ferric ammonium alum, have been measured at temperatures below 1°K using the method of γ -ray heating. The temperature measurements were made in the first instance in terms of the magnetic susceptibilities of the salts, the relation of the susceptibility to the absolute temperature having been determined for each salt in earlier experiments. The γ -ray heatings gave the specific heat in arbitrary units. The absolute values of the specific heats were found by extrapolating the results of paramagnetic relaxation measurements at higher temperatures. The measured specific heat of neodymium magnesium nitrate is compared with the value calculated from paramagnetic resonance data, and good agreement is found.

scholarly journals Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage

2018 ◽  
Vol 8 (8) ◽  
pp. 1305 ◽  
Author(s):  
Hyun Kim ◽  
Byeongnam Jo
Keyword(s):  
Specific Heat ◽  
Molten Salt ◽  
Base Fluid ◽  
Solid Phase ◽  
Layer Structure ◽  
Synthesis Process ◽  
Nanoparticle Concentration ◽  
Anomalous Increase ◽  
Salt Mixtures ◽  
Graphite Nanoparticles

An anomalous increase of the specific heat was experimentally observed in molten salt nanofluids using a differential scanning calorimeter. Binary carbonate molten salt mixtures were used as a base fluid, and the base salts were doped with graphite nanoparticles. Specific heat measurements of the nanofluids were performed to examine the effects of the composition of two salts consisting of the base fluid. In addition, the effect of the nanoparticle concentration was investigated as the concentration of the graphite nanoparticles was varied from 0.025 to 1.0 wt %. Moreover, the dispersion homogeneity of the nanoparticles was explored by increasing amount of surfactant in the synthesis process of the molten salt nanofluids. The results showed that the specific heat of the nanofluid was enhanced by more than 30% in the liquid phase and by more than 36% in the solid phase at a nanoparticle concentration of 1 wt %. It was also observed that the concentration and the dispersion homogeneity of nanoparticles favorably affected the specific heat enhancement of the molten salt nanofluids. The dispersion status of graphite nanoparticles into the salt mixtures was visualized via scanning electron microscopy. The experimental results were explained according to the nanoparticle-induced compressed liquid layer structure of the molten salts.

Fragility of Metallic Glass Forming Liquids

2002 ◽  
Vol 754 ◽  
Author(s):  
G. J. Fan ◽  
R. K. Wunderlich ◽  
H.-J. Fecht
Keyword(s):  
Transition Metal ◽  
Metallic Glass ◽  
Liquid Structure ◽  
Energy Difference ◽  
Late Transition Metal ◽  
Glass Forming ◽  
Metal Type ◽  
Gibbs Free Energy Difference ◽  
Late Transition ◽  
Early Late

ABSTRACTBased on the available kinetic and thermodynamic data, we compare the kinetic fragility and thermodynamic fragility of different metallic glass forming liquids. The results indicate a correlation between the kinetic and thermodynamic fragility in metallic glass forming liquids, consistent with the energy landscape model which predicts a connection between the kinetic and thermodynamic properties of supercooled liquids. The metal - metalloid glass forming alloys such as PdNiCuP are found to exhibit a distinctively different correlation as compared to early – late transition metal – type metallic glass forming alloys such as ZrTiCuNiBe. For the same thermodynamic fragility the former exhibit a much larger kinetic fragility indicating that the two classes of alloys have a different liquid structure. In addition, the relationship between the kinetic fragility and the Gibbs free energy difference between the undercooled liquid and the crystalline phases has been discussed in both metal metalloid glass forming alloys and early - late transition metal – type metallic glass forming alloys.

Measurement of Specific Heat Using Bayesian Inference to Account for Uncertainties in the Calorimeter Performance

2006 ◽  
Author(s):  
A. F. Emery ◽  
K. Abernethy
Keyword(s):  
Thermal Conductivity ◽  
Bayesian Inference ◽  
Specific Heat ◽  
High Accuracy ◽  
Temperature History ◽  
Good Precision ◽  
Precise Characterization ◽  
Transient Conduction ◽  
Measured Specific Heat

One way of estimating thermal conductivity is to measure the temperature history for transient conduction. Unfortunately, the property estimated is usually not the conductivity but the thermal diffusivity, α = k/ρcp. While α can often be estimated with good precision, and ρ is usually well defined, the specific heat is often poorly known. As a consequence the uncertainty in the conductivity can be large. This paper reports the use of a calorimeter designed to measure the specific heat with high accuracy. The accuracy depends upon a precise characterization of the thermal performance of the calorimeter. Even when much care is taken, the calorimeter's behavior introduces uncertainty in the measured specific heat. The effects of these uncertainties are accounted for by using Bayesian inference to estimate the confidence intervals of the specific heat.

Glass Forming Ability of Ca-Based Bulk Metallic Glasses

2011 ◽  
Vol 171 ◽  
pp. 121-126 ◽  
Author(s):  
Ashmi T. Patel ◽  
Kirit N. Lad ◽  
Arun Pratap
Keyword(s):  
Metallic Glasses ◽  
Driving Force ◽  
Bulk Metallic Glasses ◽  
Energy Difference ◽  
Glass Forming Ability ◽  
Point Of View ◽  
Undercooled Liquid ◽  
Free Energy Difference ◽  
Glass Forming ◽  
Gibbs Free Energy Difference

Knowledge of glass forming ability (GFA) of amorphous metallic alloys is very important from both theoretical and practical point of view. Thermodynamically, the Gibbs free energy difference, ΔG between the undercooled liquid and the corresponding crystalline state is driving force for crystallization. As a consequence, it is a good indicator for glass forming ability of metallic glasses. A novel expression for ΔG has been used to estimate the GFA of recently developed Ca-based bulk metallic glasses viz. Ca53Mg23Cu24,Ca65Mg15Cu20,Ca40Mg25Cu35, Ca50Mg22.5Cu27.5 and Ca55Mg15Cu30. Different GFA criteria are also evaluated for systems taken up in the study and effect of addition of variation in composition of Ca-Mg-Cu system is also investigated. Present work suggests that among different GFA criteria, ΔG is the best criterion for the prediction of GFA for Ca-based bulk metallic glasses.

On metastable approximations in co-operative assemblies

1956 ◽  
Vol 235 (1201) ◽  
pp. 247-259 ◽  
Keyword(s):  
Exact Solution ◽  
Specific Heat ◽  
Curie Point ◽  
Lattice Structure ◽  
Three Dimensional ◽  
Entropy Change ◽  
Successive Approximations ◽  
Series Expansions ◽  
Temperature Expansion ◽  
Heat Curve

The exact solution of the three-dimensional Ising model of a ferromagnetic presents diffi­culties of a very fundamental nature. It therefore seems that the most reliable information on the behaviour of the model is provided by exact series expansions of the partition func­tion at low and high temperatures. However, the usual low -temperature expansion fails to converge in the neighbourhood of the critical point. By rearranging the terms of the series on the basis of physical considerations, it is possible to obtain a systematic set of successive approximations, each approximation taking exact account of clusters of a given size or less (metastable approximations). By extrapolation accurate estimates can be derived of the Curie point and critical values of the energy and entropy. It is found that there is a marked difference in behaviour between two- and three-dimensional lattices, a far larger proportion of the entropy change taking place in the temperature region below the Curie point in the latter case. The corre­sponding specific heat curves are therefore much closer to those observed experimentally. Finally, a brief discussion is given of the dependence of the specific heat curve on lattice structure.

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