Heat capacities and enthalpies of fusion and transformation for solvates of some salts with dimethyl sulfoxide and dimethylformamide

1988 ◽  
Vol 53 (12) ◽  
pp. 3072-3079
Author(s):  
Mojmír Skokánek ◽  
Ivo Sláma
Keyword(s):  
Heat Capacity ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Dimethyl Sulfoxide ◽  
Liquidus Temperature ◽  
Molar Heat Capacity ◽  
Solid Phase ◽  
Zinc Nitrate ◽  
Heat Capacities ◽  
Liquid Phases

Molar heat capacities and molar enthalpies of fusion of the solvates Zn(NO3)2 . 2·24 DMSO, Zn(NO3)2 . 8·11 DMSO, Zn(NO3)2 . 6 DMSO, NaNO3 . 2·85 DMSO, and AgNO3 . DMF, where DMSO is dimethyl sulfoxide and DMF is dimethylformamide, have been determined over the temperature range 240 to 400 K. Endothermic peaks found for the zinc nitrate solvates below the liquidus temperature have been ascribed to solid phase transformations. The molar enthalpies of the solid phase transformations are close to 5 kJ mol-1 for all zinc nitrate solvates investigated. The dependence of the molar heat capacity on the temperature outside the phase transformation region can be described by a linear equation for both the solid and liquid phases.

scholarly journals Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1147
Author(s):  
Rudolf Naef
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Goodness Of Fit ◽  
Cross Validation ◽  
Solid Phase ◽  
Linear Equations ◽  
Heat Capacities ◽  
Molecular Volume ◽  
Complementary Method ◽  
Standard Deviations

The calculation of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, applying a universal computer algorithm based on the atom-groups additivity method, using refined atom groups. The atom groups are defined as the molecules’ constituting atoms and their immediate neighbourhood. In addition, the hydroxy group of alcohols are further subdivided to take account of the different intermolecular interactions of primary, secondary, and tertiary alcohols. The evaluation of the groups’ contributions has been carried out by solving a matrix of simultaneous linear equations by means of the iterative Gauss–Seidel balancing calculus using experimental data from literature. Plausibility has been tested immediately after each fitting calculation using a 10-fold cross-validation procedure. For the heat capacity of liquids, the respective goodness of fit of the direct (r2) and the cross-validation calculations (q2) of 0.998 and 0.9975, and the respective standard deviations of 8.24 and 9.19 J/mol/K, together with a mean absolute percentage deviation (MAPD) of 2.66%, based on the experimental data of 1111 compounds, proves the excellent predictive applicability of the present method. The statistical values for the heat capacity of solids are only slightly inferior: for r2 and q2, the respective values are 0.9915 and 0.9874, the respective standard deviations are 12.21 and 14.23 J/mol/K, and the MAPD is 4.74%, based on 734 solids. The predicted heat capacities for a series of liquid and solid compounds have been directly compared to those received by a complementary method based on the "true" molecular volume and their deviations have been elucidated.

scholarly journals On the Determination of Molar Heat Capacity of Transition Elements: From the Absolute Zero to the Melting Point

2021 ◽  
Author(s):  
Ivaldo Leão Ferreira ◽  
José Adilson de Castro ◽  
Amauri Garcia
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Molar Heat Capacity ◽  
Materials Science ◽  
Solid Phase ◽  
Transition Elements ◽  
Phase Nucleation ◽  
New Formulation ◽  
Solid Liquid

Molar specific heat is one of the most important thermophysical properties to determine the sensible heat, heat of transformation, enthalpy, entropy, thermal conductivity, and many other physical properties present in several fields of physics, chemistry, materials science, metallurgy, and engineering. Recently, a model was proposed to calculate the Density of State by limiting the total number of modes by solid–liquid and solid–solid phase nucleation and by the entropy associated with phase transition. In this model, the new formulation of Debye’s equation encompasses the phonic, electronic, and rotational energies contributions to the molar heat capacity of the solids. Anomalies observed in the molar specific heat capacity, such as thermal, magnetic, configurational transitions, and electronic, can be treated by their transitional entropies. Model predictions are compared with experimental scatter for transitional elements.

scholarly journals Твердофазные реакции и фазовые превращения в наноразмерной пленочной структуре висмут/селен

2018 ◽  
Vol 52 (8) ◽  
pp. 823
Author(s):  
В.Я. Когай ◽  
Г.М. Михеев
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Film Structure ◽  
Phase Synthesis ◽  
Crystallite Sizes ◽  
Solid Phase Reactions ◽  
First Time

AbstractExperimental results of a study concerned with solid-phase reactions and phase transformations in a Bi/Se nanoscale film structure under heat treatment in vacuum are presented. Nanocrystalline Bi2Se3, BiSe, and Bi_4Se_3 films are obtained for the first time by solid-phase synthesis at various ratios between the Bi and Se layer thicknesses. The phase-transformation temperatures at which Se, BiSe, and Bi4Se3 crystalline phases are formed are determined. The average crystallite sizes in the Bi_2Se_3, BiSe, and Bi_4Se_3 films are found to be 21, 23, and 33 nm, respectively.

scholarly journals Высокотемпературная теплоемкость германатов Pr-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- и Nd-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- в области 350-1000 K

2018 ◽  
Vol 60 (3) ◽  
pp. 618
Author(s):  
Л.Т. Денисова ◽  
Л.А. Иртюго ◽  
В.В. Белецкий ◽  
Н.В. Белоусова ◽  
В.М. Денисов
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Temperature Effect ◽  
Molar Heat Capacity ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Scanning Calorimetry ◽  
Phase Synthesis

AbstractPr2Ge2O7 and Nd2Ge2O7 were obtained via solid-phase synthesis from Pr2O3 ( Nd2O3 ) and GeO2 with multistage firing in air within 1273–1473 K. A temperature effect on molar heat capacity of the oxide compounds was measured with a differential scanning calorimetry. Their thermodynamic properties were calculated from the C _ P = f ( T ) dependences.

Molar heat capacities and enthalpies of fusion for the system zinc chloride-dimethyl sulphoxide

1987 ◽  
Vol 52 (9) ◽  
pp. 2188-2193
Author(s):  
Mojmír Skokánek ◽  
Ivo Sláma
Keyword(s):  
Heat Capacity ◽  
Phase Transitions ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Zinc Chloride ◽  
Liquid State ◽  
Molar Heat Capacity ◽  
Heat Capacities ◽  
Dimethyl Sulphoxide ◽  
Molten State

Molar heat capacities and molar enthalpies of phase transitions in the system ZnCl2-DMSO have been investigated over the temperature range 240 to 405 K and the concentration range 11.1 to 40 mole % ZnCl2. The temperatures of fusion and of phase transitions were determined and compared with literature data. Equations were proposed for the description of the temperature dependence of the molar heat capacity in the liquid state. The concentration dependence of the molar heat capacity in the molten state was found to exhibit positive deviations from additivity.

scholarly journals A New Concept for Modeling Phase Transformations in Ti6Al4V Alloy Manufactured by Directed Energy Deposition

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2985
Author(s):  
Jérôme Tchoufang Tchuindjang ◽  
Hakan Paydas ◽  
Hoang-Son Tran ◽  
Raoul Carrus ◽  
Laurent Duchêne ◽  
...  
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Energy Deposition ◽  
State Of The Art ◽  
Solid Phase ◽  
Ti6al4v Alloy ◽  
3D Finite Element ◽  
Final Microstructure ◽  
Directed Energy

The microstructure directly influences the subsequent mechanical properties of materials. In the manufactured parts, the elaboration processes set the microstructure features such as phase types or the characteristics of defects and grains. In this light, this article aims to understand the evolution of the microstructure during the directed energy deposition (DED) manufacturing process of Ti6Al4V alloy. It sets out a new concept of time-phase transformation-block (TTB). This innovative segmentation of the temperature history in different blocks allows us to correlate the thermal histories computed by a 3D finite element (FE) thermal model and the final microstructure of a multilayered Ti6Al4V alloy obtained from the DED process. As a first step, a review of the state of the art on mechanisms that trigger solid-phase transformations of Ti6Al4V alloy is carried out. This shows the inadequacy of the current kinetic models to predict microstructure evolution during DED as multiple values are reported for transformation start temperatures. Secondly, a 3D finite element (FE) thermal simulation is developed and its results are validated against a Ti6Al4V part representative of repair technique using a DED process. The building strategy promotes the heat accumulation and the part exhibits heterogeneity of hardness and of the nature and the number of phases. Within the generated thermal field history, three points of interest (POI) representative of different microstructures are selected. An in-depth analysis of the thermal curves enables distinguishing solid-phase transformations according to their diffusive or displacive mechanisms. Coupled with the state of the art, this analysis highlights both the variable character of the critical points of transformations, and the different phase transformation mechanisms activated depending on the temperature value and on the heating or cooling rate. The validation of this approach is achieved by means of a thorough qualitative description of the evolution of the microstructure at each of the POI during DED process. The new TTB concept is thus shown to provide a flowchart basis to predict the final microstructure based on FE temperature fields.

scholarly journals Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of a Generally Applicable Computer Algorithm Based on the Group-Additivity Method

2020 ◽  
Author(s):  
Rudolf Naef
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Goodness Of Fit ◽  
Cross Validation ◽  
Solid Phase ◽  
Heat Capacities ◽  
Computer Algorithm ◽  
Molecular Volume ◽  
Complementary Method ◽  
Standard Deviations

The calculation of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, applying a universal computer algorithm based on the atom-groups additivity method, using refined atom groups. The atom groups are defined as the molecules' constituting atoms and their immediate neighbourhood. In addition, the hydroxy group of alcohols are further subdivided to take account of the different intermolecular interactions of primary, secondary and tertiary alcohols. The evaluation of the groups' contributions has been carried out by means of a fast Gauss-Seidel fitting calculus using experimental data from literature. Plausibility has been tested immediately after each fitting calculation using a 10-fold cross-validation procedure. For the heat capacity of liquids, the respective goodness of fit of the direct (R2) and the cross-validation calculations (Q2) of 0.998 and 0.9975, and the respective standard deviations of 8.2 and 9.16 J/mol/K, together with a medium absolute percentage deviation (MAPD) of 2.69%, based on the experimental data of 1133 compounds, proves the excellent predictive applicability of the present method. The statistical values for the heat capacity of solids are only slightly inferior: for R2 and Q2, the respective values are 0.9915 and 0.9875, the respective standard deviations are 12.19 and 14.13 J/mol/K and the MAPD is 4.65%, based on 732 solids. The predicted heat capacities for a series of liquid and solid compounds has been directly compared to those received by a complementary method based on the "true" molecular volume [1] and their deviations elucidated.

Approximation of adsorption heats of carbon monoxide on transition metals by means of an empirical model

1983 ◽  
Vol 48 (10) ◽  
pp. 2735-2739
Author(s):  
Jiří Fusek ◽  
Oldřich Štrouf ◽  
Karel Kuchynka
Keyword(s):  
Carbon Monoxide ◽  
Heat Capacity ◽  
Transition Metals ◽  
Molar Heat Capacity ◽  
Metal Adsorption ◽  
Heat Of Fusion ◽  
Class Structure ◽  
Fundamental Parameters ◽  
Adsorption Heats ◽  
Pauling Electronegativity

The class structure of transition metals chemisorbing carbon monoxide was determined by expressing the following fundamental parameters in the form of functions: The molar heat capacity, the 1st and 2nd ionization energy, the heat of fusion, Pauling electronegativity, the electric conductivity, Debye temperature, the atomic volume of metal. Adsorption heats have been predicted for twelve transition metals.

Reactivity in solid phase. Transformations of 2,4-di-tert-butylphenol and its derivatives under elastic deformation conditions

1996 ◽  
Vol 45 (6) ◽  
pp. 1428-1432
Author(s):  
V. B. Vol'eva ◽  
I. S. Belostotskaya ◽  
A. Yu. Karmilov ◽  
N. L. Komissaroya ◽  
V. V. Ershov
Keyword(s):  
Phase Transformations ◽  
Elastic Deformation ◽  
Solid Phase
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