A low-temperature technique for measuring enthalpies of formation

1996 ◽  
Vol 11 (6) ◽  
pp. 1403-1409 ◽  
Author(s):  
T. P. Weihs ◽  
T. W. Barbee ◽  
M. A. Wall
Keyword(s):  
Low Temperature ◽  
Enthalpy Of Formation ◽  
Enthalpies Of Formation ◽  
Scanning Calorimetry ◽  
Free Standing ◽  
Metal Compounds ◽  
Si Substrates ◽  
Multilayer Foils ◽  
Formation Enthalpies ◽  
The Enthalpy Of Formation

A technique to accurately measure the formation enthalpies of transition metal compounds at relatively low temperatures using thick multilayer foils and differential scanning calorimetry is demonstrated. The enthalpy of formation of Cu51Zr14 was measured using 25 μm thick, free-standing Cu–Zr multilayer foils. The multilayers were deposited onto Si substrates using a planetary, magnetron source sputtering system. They were removed from their substrates, cut into 6 mm diameter specimens, and scanned in temperature from 50 °C to 725 °C in a differential scanning calorimeter. Three distinct exothermic reactions were systematically observed. The heats from the first two reactions were summed and then analyzed using a simple model that accounts for interfacial reactions and heat losses during deposition. The enthalpy of formation for Cu51Zr14 was measured to be 14.3 ± 0.3 kJ/mol. This quantity agrees with the single value of ΔHf = 14.07 ± 1.07 kJ/mol reported in the literature for this Cu–Zr compound. The advantages of measuring formation enthalpies using thick multilayer foils and low temperature calorimetry are discussed.

scholarly journals Thermochemistry of Eight Membered Ring Hydrocarbons. The Enthalpy of Formation of Cyclooctane

2001 ◽  
Vol 71 (3) ◽  
pp. 507-515
Author(s):  
Daniela Gheorghe ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Phase ◽  
Phase Change ◽  
Enthalpy Of Formation ◽  
Membered Ring ◽  
Heat Of Combustion ◽  
Enthalpies Of Formation ◽  
Scanning Calorimetry ◽  
Solid Liquid ◽  
The Enthalpy Of Formation

A new value of the enthalpy of formation of cyclooctane (-156.2�1.2 kJ mol-1) based on heat of combustion measurements is reported. Its solid - liquid phase change was investigated by differential scanning calorimetry in both directions revealing an overcooling effect of over 23 K. Our enthalpy of formation of cyclooctane was used together with literature values of heats of hydrogenation of 8 carbon atoms cycloolefins to calculate the enthalpies of formation of the later. The strain energies of the investigated molecules were calculated and discussed.

Thermochemistry of Organic and Heteroorganic Species. Part IX. Photoionization Studies of Isomerization and Fragmentation of Polysubstituted Cyclopropenes: Phenyl-Substituted Cyclopropenes

2000 ◽  
Vol 6 (1) ◽  
pp. 53-64 ◽  
Author(s):  
V.V. Takhistov ◽  
I.N. Domnin ◽  
D.A. Ponomarev
Keyword(s):  
Mass Spectrometry ◽  
Enthalpy Of Formation ◽  
Good Alternative ◽  
Enthalpies Of Formation ◽  
Isodesmic Reactions ◽  
Ion Structure ◽  
Photoionization Mass Spectrometry ◽  
General Methodology ◽  
Fragment Ions ◽  
The Enthalpy Of Formation

Ionization and appearance energies of some fragment ions from 1,2,3-trimethy1-3-phenyl-, 3-methyl-1,2,3-triphenyl-, 1,2-diphenyl-3-methoxycarbonyl-, 1,2,3-triphenyl-3-methoxycarbonyl- and 1,3,3-triphenyl-2-methoxycarbonyl-cyclopropenes were measured by photoionization mass spectrometry. It was shown that in none of these compounds did the fragment ions possess the expected stable substituted cyclopropenium ion structure. Accordingly, possible schemes of molecular ion isomerization are given. The enthalpies of formation of nearly 50 substituted cyclopropenium ions, and ions of related structure, were estimated using series of isodesmic reactions. This publication, together with the previous works of the authors in this Journal, demonstrates the general methodology for estimation of the enthalpy of formation for even-electron ions. It is suggested that the present methodology can provide a good alternative to other estimation or computation procedures applied to the thermochemistry of ions.

scholarly journals Point Defects in Materials Part I: Behavior and Characteristics in Different Material Classes

MRS Bulletin ◽  
1991 ◽  
Vol 16 (11) ◽  
pp. 28-32
Author(s):  
David N. Seidman ◽  
Donglu Shi
Keyword(s):  
Enthalpy Of Formation ◽  
Point Defects ◽  
Theoretical Calculations ◽  
Pure Copper ◽  
Historical Review ◽  
Enthalpies Of Formation ◽  
Professor Emeritus ◽  
Face Centered Cubic ◽  
Interstitial Atoms ◽  
The Enthalpy Of Formation

In this issue of the MRS Bulletin we present five papers that involve point defect phenomena in a wide variety of materials—metals, conducting ceramic oxides, semiconductors, amorphous alloys, and high Tc superconducting oxides. The unifying theme of this issue is point defects—zero-dimensional defects. Even for the high Tc oxides, where planar defects are discussed, it is the ordering of oxygen/vacancy chains that ultimately gives rise to twins in the famous YBa2Cu3O7.δ (1:2:3) oxide superconductor.Hillard Huntington, professor emeritus of physics at Rensselaer Polytechnic Institute, is an early and important pioneer in the study of point defects in metals. A theorist, he has also performed many experiments over the years; for example, he performed key early experiments on electromigration effects. Huntington's article presents a historical review of the research on vacancies and self-interstitial atoms in metals during the period that stretches from the mid-1930s to the mid-1960s. He played a crucial role in this field as a result of his seminal theoretical calculations, with Fred Seitz in 1942, on the enthalpies of formation and migration of vacancies or self-interstitial atoms in pure copper. Huntington's and Seitz's calculations indicated that diffusion occurs predominantly by a monovacancy mechanism since the enthalpy of formation of a self-interstitial atom, the [100] split form, also called the dumbbell form, is too large to be compatible with the activation enthalpy for self-diffusion in copper. It is now well established that the latter is given by the sum of the enthalpy of formation and the enthalpy of migration of a monovacancy in many face-centered-cubic (fcc), body-centered-cubic (bec), and hexagonal-close-packed (hcp) metals.

Calorimetric Investigation of Relaxation Processes in Disordered Semiconductors

1996 ◽  
Vol 420 ◽  
Author(s):  
B. G. Budaguan ◽  
A. A. Aivazov ◽  
A. Yu. Sazonov
Keyword(s):  
Porous Silicon ◽  
Low Temperature ◽  
Electrochemical Etching ◽  
Structural Rearrangement ◽  
Endothermic Effect ◽  
Relaxation Processes ◽  
Exothermic Effect ◽  
Scanning Calorimetry ◽  
Si Substrates ◽  
Dsc Measurements

AbstractThe comparative study of relaxation processes in amorphous hydrogenated (a- Si:H) and porous silicon (PS) by use of differential scanning calorimetry (DSC) measurements is presented. Films of a-Si:H were deposited by RF glow discharge of two gas mixtures (10% SiH4+ 90% H2) and (5% SiH4 + 95% He). PS films have been prepared by electrochemical etching of 1Ω-cm (p- PS) and of 0.01Ω-cm (p+ PS) ptype Si substrates. The DSC traces were recorded during the heating of samples at a constant rate of 10°C/min from 20 to 5700C in an Ar atmosphere. All investigated samples present a low temperature exothermic effect with a maxima within 120-2800C. At higher temperatures (T>3000C) a second exothermic effect is observed for a-Si:H films prepared from both hydrogen and helium diluted silane mixtures while two endothermic effects are observed for PS samples. Analysis of the low temperature exothermic effects has been performed, and focussed on the relaxation of weak Si-Si bonds which are the features of both amorphous hydrogenated and porous silicon. It was shown that the endothermic effect connected with hydrogen effusion from PS at higher temperatures is compensated by exothermic structural rearrangement in the case of a-Si:H.

Enthalpies of formation of LaBO3perovskites (B = Al, Ga, Sc, and In)

2003 ◽  
Vol 18 (10) ◽  
pp. 2501-2508 ◽  
Author(s):  
Jihong Cheng ◽  
Alexandra Navrotsky
Keyword(s):  
High Temperature ◽  
Enthalpy Of Formation ◽  
Solution Calorimetry ◽  
Tolerance Factor ◽  
Enthalpies Of Formation ◽  
Oxide Melt ◽  
High Temperature Oxide ◽  
Temperature Oxide ◽  
First Time ◽  
The Enthalpy Of Formation

Enthalpies of formation from constituent oxides and elements at 298 K were determined by high-temperature oxide melt solution calorimetry for a group of technologically important perovskites LaBO3(B = La, Ga, Sc, and In). Enthalpies of formation from oxides of LaAlO3and LaGaO3are −69.61 ± 3.23 kJ/mol and −52.39 ± 1.99 kJ/mol, respectively. The data were consistent with literature values obtained using other methods. The enthalpies of formation of LaScO3and LaInO3from oxides were reported for the first time as −38.64 ± 2.30 kJ/mol and −23.99 ± 2.31 kJ/mol, respectively. As seen for other perovskites, as the tolerance factor deviates more from unity (in the order Al, Ga, Sc, In), the enthalpy of formation from oxides becomes less exothermic, indicating a less stable structure with respect to the constituent oxides.

Soldering and Brazing Metals to Ceramics at Room Temperature Using a Novel Nanotechnology

2006 ◽  
Vol 45 ◽  
pp. 1578-1587 ◽  
Author(s):  
A. Duckham ◽  
J. Levin ◽  
T.P. Weihs
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Thermal Stresses ◽  
Local Heat ◽  
Bonding Process ◽  
Free Standing ◽  
Multilayer Foils ◽  
Heats Of Mixing ◽  
Reactive Foils ◽  
Low Temperature Process

This paper reviews a new, low-temperature process for soldering and brazing ceramics to metals that is based on the use of reactive multilayer foils as a local heat source. The reactive foils range in thickness from 40μm to 100μm and contain many nanoscale layers that alternate between materials with large heats of mixing, such as Al and Ni. By inserting a free-standing foil between two solder (or braze) layers and two components, heat generated by the reaction of the foil melts the solder (or braze) and consequently bonds the components. The use of reactive foils eliminates the need for a furnace, and dramatically reduces the heating of the components being bonded. Thus ceramics and metals can be joined over large areas without the damaging thermal stresses that are typically encountered when cooling in furnace soldering or brazing operations. This paper draws on earlier work to review the bonding process and its application to a variety of ceramic-metal systems. Predictions of thermal profiles during bonding and the resulting residual stresses are described and compared with results for conventional soldering or brazing processes. The microstructure, uniformity, and physical properties of the reactive foil bonds are reviewed as well, using several different ceramic-metal systems as examples.

Calorimetric determination of the enthalpy of formation of InN and comparison with AlN and GaN

2001 ◽  
Vol 16 (10) ◽  
pp. 2824-2831 ◽  
Author(s):  
M. R. Ranade ◽  
F. Tessier ◽  
A. Navrotsky ◽  
R. Marchand
Keyword(s):  
Enthalpy Of Formation ◽  
Standard Enthalpy ◽  
Sodium Molybdate ◽  
Solution Calorimetry ◽  
Large Error ◽  
Area Measurement ◽  
Enthalpies Of Formation ◽  
Standard Enthalpy Of Formation ◽  
Straight Line ◽  
The Enthalpy Of Formation

The standard enthalpy of formation of InN at 298 K has been determined using high-temperature oxidative drop solution calorimetry in a molten sodium molybdate solvent at 975 K. Calorimetric measurements were performed on six InN samples with varying nitrogen contents. The samples were characterized using x-ray diffraction, chemical analysis, electron microprobe analysis, and Brunauer–Emmett–Teller surface area measurement. The variation of the enthalpy of drop solution (kJ/g) with nitrogen content is approximately linear. The data, when extrapolated to stoichiometric InN, yield a standard enthalpy of formation from the elements of ?28.6 ± 9.2 kJ/mol. The relatively large error results from the deviation of individual points from the straight line rather than uncertainties in each set of data for a given sample. This new directly measured enthalpy of formation is in good agreement with the old combustion calorimetric result by Hahn and Juza (1940). However, this calorimetric enthalpy of formation is significantly different from the enthalpy of formation values derived from the temperature dependence of the apparent decomposition pressure of nitrogen over InN. A literature survey of the enthalpies of formation of III–N nitride compounds is presented.

Thermodynamics of metal-ligand bond formation. XI. Adducts of heterocyclic bases with copper(II) complexes of fluorinated β-diketones

1974 ◽  
Vol 27 (4) ◽  
pp. 741 ◽  
Author(s):  
DP Graddon ◽  
WK Ong
Keyword(s):  
Enthalpy Of Formation ◽  
Benzene Solution ◽  
Bidentate Ligand ◽  
Molecular Structures ◽  
Enthalpies Of Formation ◽  
Complex Forms ◽  
Heterocyclic Bases ◽  
The Enthalpy Of Formation ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained for the reaction in benzene solution of copper(11) complexes of hexafluoropentanedione and three trifluorinated α-diketones with several unidentate and bidentate heterocyclic bases and terpyridine. With pyridine the hexafluoro� complex forms very stable 1 : 1 and 1 : 2 adducts. The enthalpy of adduct formation (-ΔH) is about 39 kJ mol-1 for the addition of each molecule of pyridine, about 10 kJ mol-1 more than for the formation of the 1 : 1 adduct with the acetylacetone complex. The trifluoro complexes form only 1 : 1 adducts with enthalpy of formation about 31 kJ mol-1 ; these are much more stable than Cu(acac)2(py), but the extra stability is mainly due to entropy factors. With bipyridine and phenanthroline all four fluoro complexes form very stable 1 : 1 adducts with enthalpies of formation about twice those for addition of one molecule of pyridine; this shows that two Cu-N bonds are formed. 2,9-Dimethyl-1,l0-phenanthroline forms a similar adduct, but the enthalpy of formation is much less, due to steric interference. Terpyridine forms a 1 : 1 adduct of much lower stability, probably behaving as an ortho-substituted bidentate ligand. Infrared spectra of the adducts of Cu(tfaa)2 and Cu(hfaa)2 support molecular structures in which one of the Cu-O bonds linking each β-diketone is lengthened to allow the formation of a strong pair of Cu-N bonds.

scholarly journals A Promising Thermodynamic Study of Hole Transport Materials to Develop Solar Cells: 1,3-Bis(N-carbazolyl)benzene and 1,4-Bis(diphenylamino)benzene

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 381
Author(s):  
Juan Mentado-Morales ◽  
Arturo Ximello-Hernández ◽  
Javier Salinas-Luna ◽  
Vera L. S. Freitas ◽  
Maria D. M. C. Ribeiro da Silva
Keyword(s):  
Hole Transport ◽  
Enthalpies Of Formation ◽  
Thermochemical Study ◽  
Computational Studies ◽  
Scanning Calorimetry ◽  
Gaseous State ◽  
Melting Temperatures ◽  
Micro Combustion Calorimeter ◽  
Combustion Calorimeter ◽  
The Enthalpy Of Formation

The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir’s equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the 1H and 13C spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.

Enthalpy of Formation of Rare-earth Silicates Y2SiO5 and Yb2SiO5 and N-containing Silicate Y10(SiO4)6N2

1999 ◽  
Vol 14 (4) ◽  
pp. 1181-1185 ◽  
Author(s):  
Jian-Jie Liang ◽  
Alexandra Navrotsky ◽  
Thomas Ludwig ◽  
Hans J. Seifert ◽  
Fritz Aldinger
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Enthalpy Of Formation ◽  
Temperature Drop ◽  
Solution Calorimetry ◽  
Enthalpies Of Formation ◽  
Binary Oxides ◽  
Standard Enthalpies Of Formation ◽  
Oxygen Gas ◽  
The Enthalpy Of Formation

The enthalpies of formation of two rare-earth silicates (Y2SiO5 and Yb2SiO5) and a N-containing rare-earth silicate Y10(SiO4)6N2 have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt% LiBO2·48 wt% NaBO2) solvent was used at 800 °C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y2SiO5, Yb2SiO5, and Y10(SiO4)6N2, respectively, –22868.54 ± 5.34, –22774.75 ± 8.21, and –14145.20 ± 16.48 kJ/mol from elements, and –52.53 ± 4.83, –49.45 6 ± 8.35, and –94.53 ± 11.66 kJ/mol from oxides (Y2O3 or Yb2O3, SiO2) and nitride (Si3N4). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si3N4, but the N-containing silicate may be metastable with respect to assemblages containing Y2SiO5, Si3N4, and SiO2. A linear relationship was found between the enthalpy of formation of a series of M2SiO5 silicates from binary oxides and the ionic potential (z/r) of the metal cation.

Sign in / Sign up

Export Citation Format

Share Document