scholarly journals Calorimetric Studies of Magnesium-Rich Mg-Pd Alloys

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 680
Author(s):  
Adam Dębski ◽  
Sylwia Terlicka ◽  
Władysław Gąsior ◽  
Wojciech Gierlotka ◽  
Magda Pęska ◽  
...  
Keyword(s):  
Liquid Aluminum ◽  
Formation Enthalpy ◽  
Theoretical Data ◽  
Solution Calorimetry ◽  
Palladium Alloys ◽  
Formation Enthalpies ◽  
Standard Formation Enthalpy ◽  
Drop Calorimeter ◽  
Calorimetric Studies ◽  
Concentration Of Impurities

Solution calorimetry with liquid aluminum as the bath was conducted to measure the enthalpy of a solution of magnesium and palladium as well as the standard formation enthalpies of selected magnesium-palladium alloys. These alloys were synthesized from pure elements, which were melted in a resistance furnace that was placed in a glove box containing high-purity argon and a very low concentration of impurities, such as oxygen and water vapor. A Setaram MHTC 96 Line evo drop calorimeter was used to determine the energetic effects of the solution. The enthalpies of the Mg and Pd solutions in liquid aluminum were measured at 1033 K, and they equaled −8.6 ± 1.1 and −186.8 ± 1.1 kJ/mol, respectively. The values of the standard formation enthalpy of the investigated alloys with concentrations close to the Mg6Pd, ε, Mg5Pd2, and Mg2Pd intermetallic phases were determined as follows: −28.0 ± 1.2 kJ/mol of atoms, −32.6 ± 1.6 kJ/mol of atoms, −46.8 ± 1.4 kJ/mol of atoms, and −56.0 ± 1.6 kJ/mol of atoms, respectively. The latter data were compared with existing experimental and theoretical data from the literature along with data calculated using the Miedema model.

Formation Enthalpies of Tetravalent Lanthanide Perovskites by High Temperature Oxide Melt Solution Calorimetry

2002 ◽  
Vol 718 ◽  
Author(s):  
S. V. Ushakov ◽  
J. Cheng ◽  
A. Navrotsky ◽  
J. R. Wu ◽  
S. M. Haile
Keyword(s):  
High Temperature ◽  
Rietveld Method ◽  
Thermal Analyses ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Cell Parameters ◽  
Oxide Melt ◽  
Formation Enthalpies ◽  
High Temperature Oxide ◽  
Temperature Oxide

AbstractHigh-temperature oxide melt solution calorimetry was used to measure formation enthalpies for several compositions of perovskites of nominal stoichiometry BaPrO3 and BaCeO3. Samples were synthesized from chemical solution methods followed by calcination at 1100-1300°C. PrO2 was synthesized by oxidation of Pr6O11 in an oxygen flow at 280°C. The samples were characterized by microprobe, thermogravimetric and differential thermal analyses. Cell parameters were refined by the Rietveld method. Barium excess in the samples with respect to ideal stoichiometry was detected. Drop solution enthalpies were measured in a Calvet type twin microcalorimeter, using 3Na2O·4MoO3 solvent at 702°C. Preliminary values of the formation enthalpy of BaPrO3 and BaCeO3 from oxides were -70 ±10 kJ/mol and -51 ±10 kJ/mol, respectively. They fall on the normal trend of energetics versus Goldschmidt tolerance factor and do not show any special stabilization of BaPrO3 relative to other MLnO3 perovskites.

Thermodynamic Characteristics of a Series of Antimony Compounds: Standard Formation Enthalpy of Antimony Oxychloride SbOCl

2021 ◽  
pp. 109-115
Author(s):  
A.A. Gurov ◽  
A.N. Ozhogina ◽  
S.N. Solovyev
Keyword(s):  
Aqueous Solution ◽  
Hydrochloric Acid ◽  
Reference Values ◽  
Formation Enthalpy ◽  
Thermodynamic Characteristics ◽  
Dissolution Enthalpy ◽  
Formation Enthalpies ◽  
Margin Of Error ◽  
Measurement Results ◽  
Standard Formation Enthalpy

The present work opens a series of publications devoted to the description of the results of determination or clarification of the formation enthalpies of certain antimony compounds that are of significant applied interest to science and technology. The measurement results of enthalpy of interaction crystalline SbCl3 and water with formation of crystalline SbOCl are given. On the basis of the obtained and literature data, the value of standard formation enthalpy of the product of this interaction --- antimony oxychloride SbOCl at temperature 298.15 K is calculated. This value coincided with the reference values within the margin of error. An attempt was made to determine the dissolution enthalpy of SbCl3 in a two-molar aqueous solution of hydrochloric acid: the obtained approximate value of this characteristic was --30 ± 2 kJ/mol

On the trustability of semi-empirical methods to the calculation of gas phase formation enthalpies of inorganic compounds containing heavy metals: tin borates

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Heavy Metals ◽  
Gas Phase ◽  
Phase Formation ◽  
Inorganic Compounds ◽  
Formation Enthalpy ◽  
Computational Time ◽  
Gas Formation ◽  
Formation Enthalpies ◽  
Knudsen Effusion Mass Spectrometry ◽  
Semi Empirical

<p>In the present work, are calculated the gas formation enthalpies (SE; PM3 and PM6) for tin borates: SnB<sub>2</sub>O<sub>4</sub><sup> </sup>and Sn<sub>2</sub>B<sub>2</sub>O<sub>5</sub>. The calculated values are compared with experimental ones, obtained by Knudsen effusion mass spectrometry [3]. It is shown that SE methods, besides their lower computational time consuming can, indeed, provide reliable gas phase formation enthalpy values for inorganic compounds containing heavy metals.</p>

scholarly journals Thermodynamics of Molybdenum Trioxide (MoO3) Encapsulated in Zeolite Y

2021 ◽  
Author(s):  
Xianghui Zhang ◽  
Andrew Strzelecki ◽  
Cody Cockreham ◽  
Vitaliy Goncharov ◽  
Houqian Li ◽  
...  
Keyword(s):  
Molybdenum Trioxide ◽  
Zeolite Y ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Metal Species ◽  
Enthalpies Of Formation ◽  
Host Interactions ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide

Zeolites with encapsulated transition metal species are extensively applied in the chemical industry as heterogenous catalysts for favorable kinetic pathways. To elucidate the energetic insights into formation of subnano-sized molybdenum trioxide (MoO) encapsulated/confined in zeolite Y (FAU) from constituent oxides, we performed a systematic experimental thermodynamic study using high temperature oxide melt solution calorimetry as the major tool. Specifically, the formation enthalpy of each MoO/FAU is less endothermic than corresponding zeolite Y, suggesting enhanced thermodynamic stability. As Si/Al ratio increases, the enthalpies of formation of MoO/FAU with identical loading (5 Mo-wt%) tend to be less endothermic, ranging from 61.1 ± 1.8 (Si/Al = 2.9) to 32.8 ± 1.4 kJ/mol TO (Si/Al = 45.6). Coupled with spectroscopic, structural and morphological characterizations, we revealed intricate energetics of MoO – zeolite Y guest – host interactions likely determined by the subtle redox and/or phase evolutions of encapsulated MoO.

Thermochemistry of Hf-Zirconolite, CaHf Ti2O7

1999 ◽  
Vol 556 ◽  
Author(s):  
Robert L. Putnam ◽  
Alexandra Navrotsky ◽  
Brian F. Woodfield ◽  
Jennifer L. Shapiro ◽  
Rebecca Stevens ◽  
...  
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Low Temperature ◽  
Adiabatic Calorimetry ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
Capacity Data

AbstractThe formation enthalpy, - 3752.3 ± 4.7 kJ·mol−1, of Hf-zirconolite, CaHfTi2O7, was obtained using high temperature oxide-melt solution calorimetry. Combined with heat capacity data obtained using low temperature adiabatic calorimetry we report the heat capacity (Cp) and the standard molar formation energetics (ΔH°f. elements, Δ S°T, and ΔG°f. elements)for Hf-zirconolite from T = 298.15 K to T = 1500 K. Comparison of Hf-zirconolite with Zr-zirconolite is made.

Drop Solution Calorimetric Studies of Interface Enthalpy of Cubic Silver (I) Oxide (Ag2O) Nanocrystals

2021 ◽  
Vol 878 ◽  
pp. 73-80
Author(s):  
Khansaa Al-Essa ◽  
A V Radha ◽  
Alexandra Navrotsky
Keyword(s):  
Thermodynamic Cycle ◽  
Solution Calorimetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Chemical Technique ◽  
Crystallite Sizes ◽  
Wet Chemical ◽  
Wet Chemical Technique ◽  
Calorimetric Studies

The nanoscale, cubic silver (I) oxide (Ag2O.nH2O) with different particles sizes and surface areas were synthesized by a wet chemical technique. The prepared crystallite size ranges were from (33.3±0.3 to 39.4±0.4 nm). Interface areas were estimated by comparing the surface areas measured by N2 adsorption to the crystallite sizes refined from X-ray diffraction data. The interface enthalpy of Ag2O.nH2O nanocrystal was measured using isothermal acid solution calorimetry in 25%HNO3 at 26°C. The interface enthalpy was verified by utilizing thermodynamic cycle. The enthalpies of drop solution (ΔHds) for Ag2O.nH2O are exothermic and range from (-62.228±0.197) to (-64.025±0.434 kJ/mol), while its interface enthalpy is (0.842±0.508 J/m2). This work provides the first calorimetric measurement of the interface enthalpy of nanocrystalline silver (I) oxide (Ag2O.nH2O).

Energetics of oxidation of oxynitrides: Zr–N–O, Y–Zr–N–O, Ca–Zr–N–O, and Mg–Zr–N–O

2000 ◽  
Vol 15 (11) ◽  
pp. 2558-2570 ◽  
Author(s):  
I. Molodetsky ◽  
A. Navrotsky ◽  
F. DiSalvo ◽  
M. Lerch
Keyword(s):  
Formation Enthalpy ◽  
Sodium Molybdate ◽  
Solution Calorimetry ◽  
Vacancy Formation ◽  
Stabilized Zirconia ◽  
Molten Sodium ◽  
Nitrogen Concentrations ◽  
Nitrogen Ions ◽  
Long Range Ordering ◽  
End Members

The enthalpies of oxidation, δHox, of oxynitrides YyZr1−yO2x−0.5y−2/3xNx (0.016 < x < 0.2), CayZr1−yO2x−y−2/3xNx (0.03 < x < 0.14), MgyZr1−yO2x−y−2/3xNx (0.146 < x < 0.28), and Zr–O–N (β-type and γ phases) are measured using drop solution calorimetry in molten sodium molybdate (3Na2O · 4MoO3) at 973 K. Linear relations between the enthalpy δHox and nitrogen content were found in all oxynitrides. They indicate that, within the experimental range of nitrogen concentrations, sites occupied by nitrogen ions are energetically equivalent in a given substitutional series. The enthalpies normalized per mole of nitrogen, δHnox, for compounds of Y–Zr–N–O, Ca–Zr–N–O, and Zr–N–O are similar, about −500 kJ/(mol of N). A more exothermic value of δHnox, of about −950 kJ/(mol of N), is seen in Mg–Zr–N–O compounds. The energetics of vacancy formation in zirconium oxynitrides was determined and compared to the energetics of vacancy formation in yttria- and calcia-stabilized zirconia. The enthalpy of vacancy formation (enthalpy of formation relative to end members normalized per vacancy) in zirconium oxynitrides (−190.5 ± 27.0 kJ/mol of Vö) is more exothermic than that in yttria- and calcia-stabilized zirconia (−105 ± 7.2 and −91.4 ± 3.8 kJ/mol of Vö, respectively). This is consistent with the higher tendency for long-range ordering in zirconium oxynitrides compared to stabilized zirconia. Some technological implications of the results are briefly discussed.

scholarly journals Thermochemical characterization of Ca4La6(SiO4)6(OH)2 a synthetic La- and OH-analogous of britholite: implication for monazite and LREE apatites stability

Mineralogia ◽  
2008 ◽  
Vol 39 (1-2) ◽  
pp. 41-52 ◽  
Author(s):  
Emilie Janots ◽  
Fabrice Brunet ◽  
Bruno Goffé ◽  
Christophe Poinssot ◽  
Michael Burchard ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Temperature Drop ◽  
Formation Enthalpy ◽  
Solution Calorimetry ◽  
Chemical Durability ◽  
Chemical System ◽  
Constant Composition ◽  
Nuclear Waste Forms ◽  
Low Solubility

Thermochemical characterization of Ca4La6(SiO4)6(OH)2 a synthetic La- and OH-analogous of britholite: implication for monazite and LREE apatites stabilityIn this contribution, monazite (LREEPO4) solubility is addressed in a chemical system involving REE-bearing hydroxylapatite, (Ca, LREE)10(PO4,SiO4)6(OH)2. For this purpose, a synthetic (La)- and (OH)-analogous of britholite, Ca4La6(SiO4)6(OH)2, was synthesised and its thermodynamic properties were measured. Formation enthalpy of -14,618.4±31.0 kJ·mol-1 was obtained by high-temperature drop-solution calorimetry using a Tian-calvet twin calorimeter (Bochum, Germany) at 975 K using lead borate as solvent. Heat capacities (Cp) were measured in the 143-323 K and 341-623 K ranges with an automated Perkin-Elmer DSC 7. For calculations of solubility diagrams at 298 K, the GEMS program was used because it takes into account solid solutions. In conditions representative of those expected in nuclear waste disposal, calculations show that La-monazite is stable from pH = 4 to 9 with a minimum of solubility at pH = 7. La-bearing hydroxylapatite precipitates at pH > 7 with a nearly constant composition of 99% hydroxylapatite and 1% La-britholite. Each mineral buffers solution at extremely low lanthanum concentrations (log{La} = 10-10-10-15 mol·kg-1 for pH = 4 to 13). In terms of chemical durability, both La-monazite and La-rich apatite present low solubility, a requisite property for nuclear-waste forms.

Correlation model to estimate the thermodynamic properties

2017 ◽  
Vol 16 (06) ◽  
pp. 1750050
Author(s):  
O. Yu. Goncharov
Keyword(s):  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Taylor Expansion ◽  
Estimation Error ◽  
Formation Enthalpy ◽  
Correlation Model ◽  
Entropy Formula ◽  
Analytic Relationship ◽  
Standard Formation Enthalpy

A technique for constructing the correlation dependencies of the thermodynamic properties of similar compounds was proposed. This technique is based on the Taylor expansion in the supposed analytic relationship between properties. The constructed correlation dependencies were used to estimate the thermodynamic properties of the condensed bromides and iodides of hafnium HfGn (G [Formula: see text] Br, I and [Formula: see text], 2, 3, 4) and the compounds formed in the PbO–SiO2 system. Standard formation enthalpy [Formula: see text], entropy [Formula: see text], heat capacity [Formula: see text] and temperature dependencies [Formula: see text] at temperatures T[Formula: see text][Formula: see text]k to 3000[Formula: see text]k were estimated. The standard estimation error of the thermodynamic properties of the compounds in the PbO–SiO2 system does not exceed 2% for all the estimated properties. For condensed halides, the standard estimation error was (1) [Formula: see text]% for enthalpy, (2) [Formula: see text]% for entropy, (3) [Formula: see text]% for heat capacity.

The Effect of Vacancy on the Phase Stability of TiNi Shape Memory Alloy from First-Principle Calculation

2011 ◽  
Vol 687 ◽  
pp. 528-532
Author(s):  
Bin Yue ◽  
Yan Li ◽  
Fei Zhang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Phase Stability ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Tini Alloy ◽  
First Principle ◽  
Generalized Gradient ◽  
First Principle Calculation ◽  
Formation Enthalpies

The effect of vacancy on the phase stability of TiNi shape memory alloy has been investigated by the first-principle method based on the density functional theory with generalized gradient approximation. The formation energy, formation heat, formation enthalpy per atom and density of states (DOS) of TiNi alloy with and without vacancy are calculated. The results indicate that the favorable point defect is Ni vacancy in both B2 and B19’ phases of TiNi alloy. The existence of vacancy increases the formation enthalpies per atom difference and thus decreases the phase stability. The DOS values at Fermi level of martensitic phases are lower than that of austenite phases in both perfect TiNi and TiNi with Ni vacancy, indicating the natural transformation from austenite to martensite upon cooling.

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