Thermochemical Property Data Research Articles

Estimating the thermochemical properties of trimethylaluminum for thin-film processing applications

The published thermochemical property data for vapor- and liquid-phase trimethylaluminum (TMA) monomer and dimer species are reviewed in this letter. A regression scheme is developed to estimate the missing data to produce a complete set of Gibbs-free energy of formation values over temperature ranges relevant to predicting the vapor pressure and degree of TMA dimerization within thin-film deposition gas delivery and reactor systems.

Thermodynamic assessments of the Yb–Bi and the Yb–Te systems

The Yb–Bi and the Yb–Te systems are thermodynamically assessed by CALPHAD approach based on the available experimental data including thermochemical properties and phase equilibria. All of the intermetallic phases in these two systems are treated as stoichiometric compounds due to their unnoticeable homogeneity ranges, and their formation enthalpies at 0K are calculated by the first-principles method to supplement the thermochemical property data for the present optimization. The values of the first-principles calculation are confirmed by the lattice constants and the equilibrium modulus of the compounds available from experiments. Given the asymmetric shapes of the liquidus around the compounds Yb4Bi3/YbTe in the Yb–Bi/Te phase diagrams, both the associate model and the sub-regular solution model are used to describe the Gibbs free energy of the liquid phase for the two systems. The comparison between the optimization results and the experimental data for the Yb–Bi/Te systems shows that a much better agreement is obtained by means of the associate model than the sub-regular solution model.

A never-ending search for the truth: Thermodynamics in the uncertain era of the internet

This article is based on the 20th Rossini Lecture delivered on 28 July 2014 at the opening of the 23rd International Conference on Chemical Thermodynamics in Durban, South Africa.In the last several decades, enormous progress in material and computer sciences has led, in many scientific disciplines, to fundamental improvements in experimental measurement technologies. That, in combination with new communication technologies and gradually increasing societal commitment to support public scientific research, has resulted in an unprecedented growth in the “production” of the reported experimental results. These trends together with dramatically growing demand for thermophysical and thermochemical property data related to new chemical processes and products necessitated development of dynamic methods of critical data evaluation within a framework of the concept of Global Information Systems in Science which was developed and implemented for the field of thermodynamics at the Thermodynamics Research Center (TRC) of the US National Institute of Standards and Technology (NIST). Principal advantages of this approach in comparison with the traditional static methods of critical data evaluation are illustrated.Major components of the developed system and its impact on such areas of human activities as information delivery, data publication, chemical process design, chemical product design, experiment planning, and education are discussed. The systems and software tools designed for global validation of experimental values are outlined. A variety of experimental data-driven technologies for thermophysical property prediction developed with the use of the elements of the Global Information System in Thermodynamics, including those based on surrogate mixture models, group contributions, QSPR, UNIFAC, and Monte Carlo molecular simulation, are described.

Ab Initio Kinetics for Thermal Decomposition of CH3N•NH2, cis-CH3NHN•H, trans-CH3NHN•H, and C•H2NNH2 Radicals

The thermal decomposition of the CH(3)N(•)NH(2), cis-CH(3)NHN(•)H, trans-CH(3)NHN(•)H, and C(•)H(2)NNH(2) radicals, which are the four radical products from the H-abstraction reactions of monomethylhydrazine, were theoretically studied by using ab initio Rice-Ramsperger-Kassel-Marcus (RRKM) transition-state theory and master equation analysis. Various decomposition pathways were identified by using either the QCISD(T)/cc-pV∞Z//CASPT2/aug-cc-pVTZ or the QCISD(T)/cc-pV∞Z//B3LYP/6-311++G(d,p) quantum chemistry methods. The results reveal that the β-scission of NH(2) to form methyleneimine is the predominant channel for the decomposition of the C(•)H(2)NNH(2) radical due to its small energy barrier of 13.8 kcal mol(-1). The high pressure limit rate coefficient for the reaction is fitted by 3.88 × 10(19)T(-1.672) exp(-9665.13/T) s(-1). In addition, the pressure dependent rate coefficients exhibit slight temperature dependence at temperatures of 1000-2500 K. The cis-CH(3)NHN(•)H and trans-CH(3)NHN(•)H radicals are the two distinct spatial isomers with an energy barrier of 26 kcal mol(-1) for their isomerization. The β-scission of CH(3) from the cis-CH(3)NHN(•)H radical to form trans-diazene has an energy barrier of 35.2 kcal mol(-1), and the β-scission of CH(3) from the trans-CH(3)NHN(•)H radical to form cis-diazene has an energy barrier of 39.8 kcal mol(-1). The CH(3)N(•)NH(2) radical undergoes the β-scission of methyl hydrogen and amine hydrogen to form CH(2)═NNH(2), trans-CH(3)N═NH, and cis-CH(3)N═NH products, with the energy barriers of 42.8, 46.0, and 50.2 kcal mol(-1), respectively. The dissociation and isomerization rate coefficients for the reactions were calculated via the E/J resolved RRKM theory and multiple-well master equation analysis at temperatures of 300-2500 K and pressures of 0.01-100 atm. The calculated rate coefficients associated with updated thermochemical property data are essential components in the development of kinetic mechanisms for the pyrolysis and oxidation of MMH and its derivatives.

NIST/TRC SOURCE Data Archival System: The Next-Generation Data Model for Storage of Thermophysical Properties

A new data model for storage of experimental thermophysical and thermochemical property data was developed and implemented for the NIST/TRC SOURCE data archival system. Substantial improvements in data quality, as well as system usability and extendability, are achieved. Substance identification based on chemical structures was implemented. Availability of stored chemical structures will facilitate the use of property estimation methods to supplement the experimental information.

Extension of ThermoML: The IUPAC standard for thermodynamic data communications (IUPAC Recommendations 2011)

ThermoML is an XML-based approach for storage and exchange of experimental, predicted, and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation, complex equilibria, and properties of biomaterials are described. The texts of 14 data files illustrating the new extensions are provided as Supplementary Information together with the complete text of the updated ThermoML schema.

Thermodynamic Analysis of Ash Mineral Phases in Combustion of High-Sulfur Coal with Lime

When high-sulfur coal is burnt with lime, the mineral phases of fly ash may be discussed within a SiO2−Al2O3−CaO−CaSO4 system. By obtaining the absent thermochemical property data of the key mineral 3CaO·3Al2O3·CaSO4, the quaternary system was studied thermodynamically. It has been concluded that 2CaO·SiO2 and 3CaO·3Al2O3·CaSO4 may become the dominant minerals of the fly ash if sufficient solid phase reactions can be ensured. Because 3CaO·3Al2O3·CaSO4 and 2CaO·SiO2 are both important cement minerals, there will be great potential to improve the ash characteristics in combustion of high-sulfur coal. This finding gives substantial support to our previous studies of cement clinker cogeneration in pulverized coal combustion boilers. The results will also be very helpful to study the sulfur fixation in high-temperature combustion for which the formation of 3CaO·3Al2O3·CaSO4 is critical. In addition, the knowledge of the mechanism for involved chemical reactions may benefit the production of sulfoaluminate cement as well as the modification of portland cement.

ThermoML: an XML-Based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 5. Speciation and Complex Equilibria

ThermoML is an XML-based approach for storage and exchange of measured and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation and complex equilibria are described. The text of ThermoML (xml) is provided to illustrate application of the new extensions. These are provided as Supporting Information together with the complete updated ThermoML schema.

Experiments and Modeling of Ash Mineral Evolution in Burning High-Sulfur Coal with Lime

The mineral phase evolution of ash was studied when high-sulfur coal was burnt with CaO at different proportions. Experiments were carried out in a drop-tube furnace. Modeling via FACTSAGE was performed by obtaining the absent thermochemical property data of the key mineral 3CaO·3Al 2 O 3 · CaSO 4 and expanding the database. It was found that the ash mineral phases follow a certain rule to evolve and have an immense potential for modification. At low CaO proportion, 2CaO·Al 2 O 3 ·SiO 2 might be the dominant mineral phase in ash. However, with the increase of CaO addition, the amount of 2CaO·Al 2 O 3 · SiO 2 may decrease and the amount of 2CaO·SiO 2 and 3CaO·3Al 2 O 3 ·CaSO 4 may increase noticeably. Owing to the excellent hydraulic characteristics of the latter two minerals, coal ash is very possible to become cement-like. The findings may open up an efficient way to burn the high-sulfur coal. The burning of high-sulfur coal with lime may result in an attractive sulfur fixation as well as a high-quality byproduct.

ThermoML—An XML-Based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 4. Biomaterials

ThermoML is an extensible markup language (XML)-based approach for storage and exchange of experimental and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of properties of biomaterials are described. The texts of several data files illustrating the new extensions are provided as Supporting Information together with the complete text of the updated ThermoML schema.

Web Thermo Tables - an On-Line Version of the TRC Thermodynamic Tables.

It has long been understood that availability of thermophysical and thermochemical property data is vital to scientific research and industrial design. For over 65 years, the Thermodynamics Research Center (TRC) has been publishing tables of critically evaluated data covering physical and thermodynamic properties of pure compounds, TRC Tables-Hydrocarbons and TRC Tables-Non-Hydrocarbons. Over their long history, the TRC Tables have always been valued as a reputable source of evaluated thermophysical and thermodynamic data. To facilitate more flexible, convenient, and up-to-date access to the data, here, we present the release of the on-line version of the TRC tables, Web Thermo Tables (WTT). Presently, WTT contains data for 7838 compounds and over 950,000 evaluated data points. The tabulated information includes critical properties, vapor pressures and boiling temperatures, phase transition properties, volumetric properties, heat capacities and derived properties, transport properties, reaction state-change properties, as well as index of refraction, surface tension, and speed of sound. Various search options and data plotting capabilities are provided via the Web interface. WTT are distributed through the NIST Standard Reference Data Program [1].

Thermodynamic Properties (Enthalpy, Bond Energy, Entropy, and Heat Capacity) and Internal Rotor Potentials of Vinyl Alcohol, Methyl Vinyl Ether, and Their Corresponding Radicals

Vinyl alcohols (enols) have been discovered as important intermediates and products in the oxidation and combustion of hydrocarbons, while methyl vinyl ethers are also thought to occur as important combustion intermediates. Vinyl alcohol has been detected in interstellar media, while poly(vinyl alcohol) and poly(methyl vinyl ether) are common polymers. The thermochemical property data on these vinyl alcohols and methyl vinyl ethers is important for understanding their stability, reaction paths, and kinetics in atmospheric and thermal hydrocarbon-oxygen systems. Enthalpies , entropies , and heat capacities (C(p)()(T)) are determined for CH(2)=CHOH, C(*)H=CHOH, CH(2)=C(*)OH, CH(2)=CHOCH(3), C(*)H=CHOCH(3), CH(2)=C(*)OCH(3), and CH(2)=CHOC(*)H(2). Molecular structures, vibrational frequencies, , and C(p)(T) are calculated at the B3LYP/6-31G(d,p) density functional calculation level. Enthalpies are also determined using the composite CBS-Q, CBS-APNO, and G3 methods using isodesmic work reactions to minimize calculation errors. Potential barriers for internal rotors are calculated at the B3LYP/6-31G(d,p) level and used to determine the hindered internal rotational contributions to entropy and heat capacity. The recommended ideal gas phase values calculated in this study are the following (in kcal mol(-1)): -30.0, -28.9 (syn, anti) for CH(2)=CHOH; -25.6, -23.9 for CH(2)=CHOCH(3); 31.3, 33.5 for C(*)H=CHOH; 27.1 for anti-CH(2)=C(*)OH; 35.6, 39.3 for C(*)H=CHOCH(3); 33.5, 32.2 for CH(2)=C(*)OCH(3); 21.3, 22.0 for CH(2)=CHOC(*)H(2). Bond dissociation energies (BDEs) and group additivity contributions are also determined. The BDEs reveal that the O-H, O-CH(3), C-OH, and C-OCH(3) bonds in vinyl alcohol and methyl vinyl ether are similar in energy to those in the aromatic molecules phenol and methyl phenyl ether, being on average around 3 kcal mol(-1) weaker in the vinyl systems. The keto-enol tautomerization enthalpy for the interconversion of vinyl alcohol to acetaldehyde is determined to be -9.7 kcal mol(-1), while the activation energy for this reaction is calculated as 55.9 kcal mol(-1); this is the simplest keto-enol tautomerization and is thought to be important in the reactions of vinyl alcohol. Formation of the formyl methyl radical (vinoxy radical/vinyloxy radical) from both vinyl alcohol and methyl vinyl ether is also shown to be important, and its reactions are discussed briefly.

XML-based IUPAC standard for experimental, predicted, and critically evaluated thermodynamic property data storage and capture (ThermoML) (IUPAC Recommendations 2006)

Abstract ThermoML is an Extensible Markup Language (XML)-based new IUPAC standard for storage and exchange of experimental, predicted, and critically evaluated thermophysical and thermochemical property data. The basic principles, scope, and description of all structural elements of ThermoML are discussed. ThermoML covers essentially all thermodynamic and transport property data (more than 120 properties) for pure compounds, multicomponent mixtures, and chemical reactions (including change-of-state and equilibrium reactions). Representations of all quantities related to the expression of uncertainty in ThermoML conform to the Guide to the Expression of Uncertainty in Measurement (GUM). The ThermoMLEquation schema for representation of fitted equations with ThermoML is also described and provided as supporting information together with specific formulations for several equations commonly used in the representation of thermodynamic and thermophysical properties. The role of ThermoML in global data communication processes is discussed. The text of a variety of data files (use cases) illustrating the ThermoML format for pure compounds, mixtures, and chemical reactions, as well as the complete ThermoML schema text, are provided as supporting information.

Global communications and expert systems in thermodynamics: Connecting property measurement and chemical process design

Abstract Unprecedented growth in the number of custom-designed software tools for engineering applications has created an interoperability problem between the formats and structures of thermodynamic data files and required input/output structures designed for application software products. Various approaches for standardization of thermophysical and thermochemical property data storage and exchange are analyzed in this paper. Emphasis is made on the development of the XML-based IUPAC standard for thermodynamic data communications: ThermoML. A new process for global data submission and dissemination in the field of thermodynamics based on ThermoML and Guided Data Capture software is described. Establishment of the global submission and dissemination process for thermodynamic data lays the foundation for implementation of the new concept of dynamic data evaluation formulated at NIST/TRC, which requires the development of large electronic databases capable of storing essentially all “raw” experimental data known to date with detailed descriptions of relevant metadata and uncertainties. The combination of these databases with expert software designed primarily to generate recommended data based on available “raw” experimental data and their uncertainties leads to the possibility of producing data compilations automatically “to order”, forming a dynamic data infrastructure. Implementation of the dynamic data evaluation concept for pure compounds in the new NIST/TRC ThermoData Engine software is discussed.

ThermoMLAn XML-Based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 3. Critically Evaluated Data, Predicted Data, and Equation Representation

ThermoML is an XML-based approach for storage and exchange of experimental and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of predicted data, critically evaluated data, and data expressed as equations are described. The present role of ThermoML in global data submission and dissemination is discussed with particular emphasis on cooperation between major journals in the field and TRC at NIST. The text of several data files illustrating the new extensions is provided as Supporting Information together with the complete updated ThermoML schema text.

ThermoMLAn XML-Based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 2. Uncertainties

ThermoML is an XML-based approach for storage and exchange of experimental and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the expression of uncertainties are described. Basic principles, scope, and description of all new structural elements are discussed. Representation of upper and lower limits for property values is also addressed. ThermoML covers essentially all experimentally determined thermodynamic and transport property data (more than 120 properties) for pure compounds, multicomponent mixtures, and chemical reactions (including change-of-state and equilibrium). Properties of polymers and radicals and some properties of ionic systems are not represented at present. The present role of ThermoML in global data submission and dissemination is discussed with particular emphasis on cooperation between major journals in the field and the Thermodynamics Research Center (TRC) at the National Institute of Standards and Technology. The text of several data files illustrating the expression of uncertainties in ThermoML format for pure compounds, mixtures, and chemical reactions are provided as Supporting Information, as well as the complete updated ThermoML schema text.

ThermoMLAn XML-Based Approach for Storage and Exchange of Experimental and Critically Evaluated Thermophysical and Thermochemical Property Data. 1. Experimental Data

ThermoML is an XML-based approach for storage and exchange of experimental and critically evaluated thermophysical and thermochemical property data. The basic principles, scope, and description of all structural elements of ThermoML are discussed. ThermoML covers essentially all experimentally determined thermodynamic and transport property data (more than 120 properties) for pure compounds, multicomponent mixtures, and chemical reactions (including change-of-state and equilibrium). The primary focus at present is molecular compounds. Although the focus of ThermoML is properties determined by direct experimental measurement, ThermoML does cover key derived property data such as azeotropic properties, Henry's Law constants, virial coefficients (for pure compounds and mixtures), activities and activity coefficients, fugacities and fugacity coefficients, and standard properties derived from high-precision adiabatic heat-capacity calorimetry. The role of ThermoML in global data submission and dissemination is...

Windows-based guided data capture software for mass-scale thermophysical and thermochemical property data collection.

Guided data capture software (GDC) is described for mass-scale abstraction from the literature of experimental thermophysical and thermochemical property data for organic chemical systems involving one, two, and three components, chemical reactions, and chemical equilibria. Property values are captured with a strictly hierarchical system based upon rigorous application of the thermodynamic constraints of the Gibbs phase rule with full traceability to source documents. Key features of the program and its adherence to scientific principles are described with particular emphasis on data-quality issues, both in terms of data accuracy and database integrity.

Performance and Properties of a Solid Amine Sorbent for Carbon Dioxide Removal in Space Life Support Applications

NASA is currently using a solid amine sorbent known as HSC+ for regeneratively removing CO2 in space shuttle applications. This sorbent may also be of value for CO2 removal in various industrial processes such as greenhouse gas control, industrial syntheses, and natural gas purification. To design novel sorbents and to design a CO2 scrubber based on HSC+, physical and thermochemical property data are required. In this paper, we present a detailed experimental investigation of property data and long-term performance results using HSC+ as a CO2 sorbent. Differential scanning calorimetry was used to determine the heat capacity of the material. Cyclic and equilibrium capacities of the material for CO2 pickup were determined and long-term test data show excellent performance. In addition, we have determined the heat of adsorption associated with CO2 pickup by HSC+ and the effect of moisture, using isothermal flow calorimetry. We have also performed thermal gravimetric analyses on the materials to gain insight into the stability of the material and determine the temperatures at which CO2 and constituents of HSC+ leave the surface of the material.

Window-Based Applications of TRC Databases: Structure and Internet Distribution

Thermophysical and thermochemical property data on organic compounds provide vital background information for scientific and engineering communities in both academic and industrial environments. The Thermodynamics Research Center (TRC) has collected an enormous amount of property data over the past 55 years. New advances in computer technology enable relatively large databases to have friendly “communications” based upon a PC Windows platform. Here we discuss the structure, upgrade procedures, and mechanisms for distribution over local PC networks and the Internet, with emphasis on three databases: TRC COMPOUNDS (Wincmp), SOURCE (WinSource), the archive of raw experimental data, and TRC TABLE (WinTable), the TRC collection of recommended data.