PHASE TRANSITIONS IN MULTIMOLECULAR LAYERS OF ADSORBED NITROGEN

1952 ◽  
Vol 30 (11) ◽  
pp. 890-903 ◽  
Author(s):  
J. A. Morrison ◽  
L. E. Drain ◽  
J. S. Dugdale
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Solid Phase ◽  
Melting Process ◽  
Adsorbed Films ◽  
Adsorbed Nitrogen ◽  
Normal Melting Point ◽  
Solid Phase Transition ◽  
Molecular Layers

The heat capacity of nitrogen adsorbed on titanium dioxide has been measured for amounts adsorbed corresponding to 2.2, 3.1, 4.0, and 4.8 molecular layers in the temperature range 14 ° to 75 °K. The occurrence in the adsorbed films of melting and of the transition in the solid phase of nitrogen is shown by maxima in the heat capacity. The melting process is completely reversible and takes place at temperatures below the normal melting point. The solid phase transition does not occur reversibly, the magnitude of the anomaly in the heat capacity depending upon the extent to which the system has been cooled prior to the measurement of the heat capacity. The experimental results are discussed in terms of current thermodynamic treatments of phase transitions in adsorbed films.

DSC Investigations of the Phase Transitions of [M(H2O)6](NO3)2 , where M = Mn, Co, Ni, Cu and Zn

1999 ◽  
Vol 54 (10-11) ◽  
pp. 595-598
Author(s):  
E. Mikuli ◽  
A. Migdał-Mikuli ◽  
S. Wróbel ◽  
B. Grad
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Phase ◽  
Melting Process ◽  
Melting Points ◽  
Two Stage ◽  
Two Phase ◽  
Solid Phase Transition ◽  
Cu And Zn

The phase transitions of [M(H2O)6 ](NO3)2 , where M = Mn2+ , Co2+ , Ni2+ , Cu2+ or Zn2+ have been studied at 100 -400 K by DSC. Two phase transitions connected with a two-stage melting process have been found for these five compounds. For the compound with M = Co, besides the two melting points a solid-solid phase transition at 272 K has been found.

scholarly journals Исследование кинетики фазового перехода I рода в тетракозане С-=SUB=-24-=/SUB=-Н-=SUB=-50-=/SUB=- методом ИК-Фурье спектроскопии

2019 ◽  
Vol 61 (10) ◽  
pp. 1831
Author(s):  
В.А. Марихин ◽  
С.А. Гурьева ◽  
Л.П. Мясникова ◽  
Б.З. Волчек ◽  
Д.А. Медведева
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
Narrow Temperature Interval ◽  
Solid Phase Transition ◽  
First Order Phase ◽  
Kinetics Of ◽  
Symmetry Change

The kinetics of the structural first order phase transition in the tetracosane С24Н50 monodisperse samples is studied with the help of FTIR spectroscopy. The temperature dependencies of the frequency and intensity of rocking (ν~ 720 cm-1) and bending (ν~ 1470 cm-1) vibrations of СН2-groupes in the methylene trans-sequences in the crystalline cores of the elementary lamellae are investigated. It is shown that the first order solid phase transition is developing on a heterogeneous mechanism in the narrow temperature interval (T~ 2 K) according to the theory of the diffused first order phase transitions and is due to the crystalline cell symmetry change.

Polymorphism and solid-to-solid phase transitions of a simple organic molecule, 3-chloroisonicotinic acid

CrystEngComm ◽  
2015 ◽  
Vol 17 (11) ◽  
pp. 2389-2397 ◽  
Author(s):  
Sihui Long ◽  
Panpan Zhou ◽  
Sean Parkin ◽  
Tonglei Li
Keyword(s):  
Phase Transition ◽  
Thermal Properties ◽  
Phase Transitions ◽  
Organic Molecule ◽  
Solid Phase ◽  
Molecular Symmetry ◽  
Chlorine Substitution ◽  
Solid Phase Transition

Three polymorphs have been discovered for 3-chloroisonicotinic acid. Its thermal properties appear to be eventful, including sublimation, melting and recrystallization, and solid-to-solid phase transition. The polymorphism seemingly results from the disruption of molecular symmetry by chlorine substitution.

Temperature Dependence of the Vibrational Spectra of Thallium(I) Alkanoates

1994 ◽  
Vol 48 (3) ◽  
pp. 338-344 ◽  
Author(s):  
M. V. García ◽  
M. I. Redondo ◽  
F. L. López de la Fuente ◽  
J. A. R. Cheda ◽  
E. F. Westrum ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Phase Transitions ◽  
Infrared Spectra ◽  
Solid Phase ◽  
Melting Process ◽  
Isotropic Liquid ◽  
Alkyl Chains ◽  
Enhanced Sensitivity ◽  
Conformational Order ◽  
Heat Capacity Changes

IR spectroscopy has been used to model the stepwise melting process of nine T1(I) n-alkanoate salts from the solid phase into the isotropic liquid. This study has provided an explanation of the thermal effect observed by differential scanning and adiabatic calorimetry as an enhancement in the normal sigmate shape heat-capacity morphology. Infrared spectra show that these salts exist at low temperature as crystals with a subcell different from orthorhombic or monoclinic formation (no factor group splitting observed). In the lowest solid-to-solid phase transitions, the alkyl chains remain, mainly, in a totally trans-planar conformation, but the concentration of nonplanar conformers increases continuously as the temperature rises, and at a particular value (different for each compound), the CH2 wagging progression bands disappear. The temperature range at which this chain “melting” takes place coincides with the final steps of the calorimetric enhancement of the heat capacity. Changes in wavenumbers of some characteristic bands are observed in the infrared spectra at several phase transitions found by calorimetry. Because of its enhanced sensitivity to conformational order, Raman spectroscopy also was used for several alkanoate salts.

Solidification of Ionic Liquids: Theory and Techniques

2010 ◽  
Vol 63 (4) ◽  
pp. 544 ◽  
Author(s):  
Anja-Verena Mudring
Keyword(s):  
Phase Transition ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Solid Phase ◽  
Soft Materials ◽  
Separation Science ◽  
Vast Number ◽  
Plastic Crystals ◽  
Thermal Fluids ◽  
Solid Phase Transition

Ionic liquids (ILs) have become an important class of solvents and soft materials over the past decades. Despite being salts built by discrete cations and anions, many of them are liquid at room temperature and below. They have been used in a wide variety of applications such as electrochemistry, separation science, chemical synthesis and catalysis, for breaking azeotropes, as thermal fluids, lubricants and additives, for gas storage, for cellulose processing, and photovoltaics. It has been realized that the true advantage of ILs is their modular character. Each specific cation–anion combination is characterized by a unique, characteristic set of chemical and physical properties. Although ILs have been known for roughly a century, they are still a novel class of compounds to exploit due to the vast number of possible ion combinations and one fundamental question remains still inadequately answered: why do certain salts like ILs have such a low melting point and do not crystallize readily? This Review aims to give an insight into the liquid–solid phase transition of ILs from the viewpoint of a solid-state chemist and hopes to contribute to a better understanding of this intriguing class of compounds. It will introduce the fundamental theories of liquid–solid-phase transition and crystallization from melt and solution. Aside form the formation of ideal crystals the development of solid phases with disorder and of lower order like plastic crystals and liquid crystals by ionic liquid compounds are addressed. The formation of ionic liquid glasses is discussed and finally practical techniques, strategies and methods for crystallization of ionic liquids are given.

Sign in / Sign up

Export Citation Format

Share Document