Analysis Of Thermal Parameters Research Articles

Modèle de cinétique de cristallisation en régime dynamique dans les solides amorphes

The normal interpretation of kinetic parameters in thermal analysis (DTA, TG) are deduced from isothermal experiments. In the present work, we propose a method which takes into account non-isothermal conditions, particularly high heating rates are considered. The new basic equation for the reaction rate includes in the Arrhenius relation the number of nuclei per unit volume in the sample at temperatureT. This number is a function of the heating ratev. This model allows, in particular, to account for the curvature of the variation of ln (v/T 2c ) as a function of the inverse of the crystallization peak temperature (1/Tc) for high heating rates in DTA experiments. This model is applied successfully to DTA results on an amorphous CdGeAs2 compound.

Crystal structure studies of Group V chalcogenide compounds. I. The structure of tricyclohexylphosphine sulphide

Crystals of tricyclohexylphosphine sulphide, C18H33PS, are orthorhombic, a = 10.906(2), b = 15.836(2), c = 10.362(2) Å, Z = 4, space group Pn21a. The structure was solved by direct methods and refined by full-matrix least-squares procedures to a final Rω of 0.058 for all 1209 reflexions with sin θ/λ ≤ 0.5377.Although second harmonic generation unambiguously established the correct space group as Pn21a, parameters reported here refer to the centrosymmetric space group Pnma. The geometry at phosphorus is approximately tetrahedral with an average P—C distance of 1.838(2) Å. Angles at phosphorus range from 105.4° to 113.2°. The P=S bond length of 1.966(2) Å is one of the longest bonds of this type so far reported. Rigid body analysis of thermal parameters suggests that the 'true' bond lengths are even longer.

The crystal and molecular structure of the cis-dimer of acenaphthylene

The crystal structure of the cis-dimer of acenaphthylene, C24H16, has been determined by three-dimensional X-ray analysis (R=0-070 for 950 reflexions). The space group is monoclinic P21/c with a= 11-966 (5), b= 13.930 (5), c= 10.003 (3)/~ t = 1077 (1), Z=4, Dx= 1.24, Dm= 126 g.cm-3. The bond lengths in the naphthalene rings are not significantly different from those in naphthalene itself or acenaphthene. The cyclobutane single bonds of 1.56/~ are greater than a normal single bond. The molecular symmetry deviates from mm2 by a small but significant amount. A large ring-bending amplitude of vibration of the cyclobutane ring is indicated by the analysis of thermal parameters. All measurements were at 22°C.