scholarly journals 1H NMR and Differential Scanning Calorimetry Studies on Molecular Motions and Phase Transitions in Butylammonium Bromide

1984 ◽  
Vol 57 (10) ◽  
pp. 2802-2808 ◽  
Author(s):  
Shin-ichi Fukada ◽  
Ryuichi Ikeda ◽  
Daiyu Nakamura
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
1H Nmr ◽  
Molecular Motions ◽  
Scanning Calorimetry

Differential scanning calorimetry of phase transitions in (CnH2n+1NH3)2MnCl4 compounds

1975 ◽  
Vol 17 (10) ◽  
pp. 1221-1222 ◽  
Author(s):  
E.H. Bocanegra ◽  
M.J. Tello ◽  
M.A. Arriandiaga ◽  
H. Arend
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Scanning Calorimetry

Differential Scanning Calorimetry (DSC)

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Small Samples ◽  
Calorimetric Data ◽  
Scanning Calorimetry ◽  
The Difference ◽  
Temperature Dependent Properties ◽  
Differential Scanning Calorimeters ◽  
New Applications ◽  
User Friendly

Physical and chemical changes may often be induced by raising or lowering the temperature of a substance. Typical examples are phase transitions, such as fusion, or chemical reactions, such as the solid state polymerization of sodium chloroacetate, which has an onset at 471 K: ClCH2COONa (cr) ⇋ NaCl (cr) + 1/n − (CH2COO)n − (pol) Differential scanning calorimetry (DSC) was designed to obtain the enthalpy or the internal energy of those processes and also to measure temperature-dependent properties of substances, such as the heat capacity. This is done by monitoring the change of the difference between the heat flow rate or power to a sample (S) and to a reference material (R), ΔΦ = ΦS − ΦR = (dQ/dt)S − (dQ/dt)R, as a function of time or temperature, while both S and R are subjected to a controlled temperature program. The temperature is usually increased or decreased linearly at a predetermined rate, but the apparatus can also be used isothermally. In some cases DSC experiments may provide kinetic data. According to Wunderlich, differential scanning calorimeters evolved from the differential thermal analysis (DTA) instruments built by Kurnakov at the beginning of the twentieth century. In these early DTA apparatus, the temperature difference between a sample and a reference, simultaneously heated by a single heat source, was measured as a function of time. No calorimetric data could be derived, and the instruments were used, for example, to determine the temperatures of phase transitions and to identify metals, oxides, minerals, soils, and foods. The attempts to obtain calorimetric data from DTA instruments eventually led to the development of DSC. The term differential scanning calorimetry and the acronym DSC were coined in 1963 when the first commercial instrument of this type became available. This apparatus was easy to operate, enabled fast experiments, and required only small samples (typically 5–10 mg). Its importance for materials characterization was immediately demonstrated and the DSC technique soon experienced a boom. New user-friendly commercial instruments were developed, and new applications were explored. It is, however, somewhat ironic that the method ows its still growing popularity to analytical rather than calorimetric uses.

scholarly journals Phase Polymorphism of [Co(DMSO)6](BF4)2 Studied by Differential Scanning Calorimetry

2006 ◽  
Vol 61 (3-4) ◽  
pp. 180-188 ◽  
Author(s):  
Anna Migdał-Mikuli ◽  
Łukasz Skoczylas ◽  
Elżbieta Szostak
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Melting Point ◽  
Title Compound ◽  
Metastable Phases ◽  
Scanning Calorimetry ◽  
Phase Polymorphism ◽  
Solid Phases ◽  
High Degree ◽  
Dynamical Disorder

Five solid phases of [Co(DMSO)6](BF4)2 have been detected by differential scanning calorimetry (DSC). Phase transitions were detected between the following solid phases: stable KIb↔ stable KIa at T̅C4 = (328±2) K, metastable KIII ↔ undercooled phase K0 at T̅C3 = (383±4) K, metastable KII ↔ undercooled K0 at T̅C2 = (399±2) K and stable KIa ↔ stable K0 at T̅C1 = (404±1) K. The title compound melts at Tm = 440 K. From the entropy changes at the melting point and at phase transitions it can be concluded that the phases K0 and undercooled K0 are orientationally dynamically disordered crystals. The stable phases KIa, KIb are ordered solid phases. The metastable phases KII and KIII are probably solid phases with a high degree of orientational dynamical disorder

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